Audionuts chemistry lesson - The Planted Tank Forum
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post #1 of 14 (permalink) Old 09-26-2015, 08:32 AM Thread Starter
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Audionuts chemistry lesson

I've been annoying enough people on these forums, I figured it was time to share some of what I'm doing.

This tank is basically a lesson in chemistry, and a practice tank for all of the mistakes I'll make while learning the chemistry. So far I haven't lost any life to water quality, but I have lost some life to stupidity, and a lack of control of mechanical aspects, such as the overflow.

The end goal is a Discus tank (gotta keep the missus happy) that is somewhat maintenance free. The idea of daily 50% water changes is not exciting at all.

This is the tank as it stands now. You can see the pH and ORP meter above left. On the left hand side is the overflows and return, and on the right hand side is 1800LPH canister inlet and return, with drip feed just above the canister inlet.

There's still some slight cloudiness (in this image) in the water from the recent move. I'll update as I go along.

Here is an old image of the sump setup.

The sumps sole purpose is to hold water. The tank itself is 180L, with each black tub holding 140L. This allows heavy stocking in the tank, while still maintaining a decent bio-load from a water standpoint. The sumps provide some manner of mechanical filtration due to the flow rate arrangement. The flow rate is fast out of the tank and slow in the sumps, which allows particles to sink while in the slow flow rate of the sumps. I love the idea of dosing into the sumps also, since it's a (somewhat) gradual TDS increase in the tank.

I have successfully relied solely on the surface area of the tank, plants, gravel, pipes, sumps etc for biological filtration, but since I added the canister filter for fine mechanical filtration, I've also added some biological filtration.

There's 700watts of heating in the sumps controlled by this controller.

An image of the CO2 setup with insulated CO2 tank to help minimise temperature fluctuations, and hence, pressure fluctuations.

I was using a solenoid with the pH controller to control CO2, but I've since moved to manual control which I'll explain in a bit.

I've recently moved the tank downstairs to a colder area of the house (it gets hot here in Queensland) which has the added benefit of easy drip water changes. The drip water comes form a rainfall tank which has some concrete inner lining, meaning the TDS is around 42ppm depending on length of time between rain. I've measured the water as 1.5 GH and 1.25 KH, and there's bound to be some trace elements from the metal roof, drain pipes etc.

The drip water has been a godsend. It's a cold water source so will help with temperature when it really starts getting hot here. No more water changes (YAY). As the drip water enters the tank, since it's colder, it should sink towards the bottom of the tank, which should help to ensure maximum old water exiting through the overflows. The biggest aspect from a chemistry standpoint though has been the ability to maintain a very consistent carbonate hardness. I cover this off with shell grit. Since the water is currently at pH 5.9, it does a good job of dissolving the CaCO3 rather quickly. Believe it or not, I'm currently running a 1.7pH drop between the tank water and degassed tank water. I have taken it as far as a full 2.0 pH drop with no noticeable sings of distress*. For whatever it's worth, I'm around 1500 feet above sea level. Don't even get me started on the whole this is how much CO2 you have, it's been doing my head in. I'm not interested in hearing results based on some bloody chart, nor for that matter based on pH drop. If someone does know an accurate way of determining CO2 concentration, I'm all ears. One of my goals is determining an accurate method of CO2 concentration without expensive professional meters.

*Even if I've missed the signs of distress, by all accounts, everything should be dead.

I'm currently maintaining 60ppm (3.36 dKH) of KH through a balancing act of shell grit dissolution with fresh water injection. So as the lower KH water enters the tank, the shell grit dissolves at a rate which maintains a net KH. Since the solenoid died, I've been maintaining manual CO2 control, and since I've balanced the KH, I haven't had to adjust the CO2 injection at all, pH has stayed within 0.2 points.

The excess water drains outside to a soon to setup garden.

Since I've had the drip system running I haven't seen any signs of GSA, even though I haven't yet raised the phosphate levels to my preferred 4-5ppm. Previously, within a week (of clean and water change) I would see GSA slowly start to appear. Now that I think about it, I haven't seen BBA either, and this was something I was struggling with.

I have two T5HO 4ft lights with an arctic blue light or something or another, and a tropical pink light trying to maximise red and blue spectrum's. Initially the removal of the sun (green) bulb was very noticeable from a viewing standpoint, by lighting looks very natural now (probably just used to it). The lights are currently on for nine hours, which was probably to long (hence the algae problems). But I would ideally like the lights on longer for viewing, so if other methods can control the algae I'll attempt to increase the light period again.

I've been dosing full EI, with allowances for nitrate from bioload and the such, and have been fine tuning some things since starting the drip feed. I'm currently maintaining pretty good loss of nutrients from the drip feed, but I don't like the idea of fairly large fluctuations between dosings. In other words, I dose, TDS increases, TDS decreases over time with drip feed until the next dose. My next plan of attack is to setup a DIY auto dosing of the nutrients into the tank. Then I should be able to maintain nutrient levels in the same manner that I maintain KH. Consistency being the key. One less thing I'll have to worry about every morning too.

I'm not loaded with cash, hence trying to do everything DIY where possible. At some stage in the future (after I can control water as I want) I'll place some effort into aesthetics.

Anyway, that's it for now. For anyone really interested, I maintain a spreadsheet of my tinkering here. September is where I really started to get things under control, the first few months are just a lesson in how to make mistakes.
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Last edited by Audionut; 09-26-2015 at 08:52 AM. Reason: Some spelling
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post #2 of 14 (permalink) Old 09-26-2015, 09:12 AM
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I don't think the chemistry lessons are annoying at all. I really like them.

Just skimmed through as I am tired right now, but will read through later.

What size tank is the Discus tank?
Remember Discus require temps higher temps so plant selection is limited.

I like the idea of insulating the co2 tank, haven't seen that done before.

About low pH, I recall something I read about too low of a pH (might of been more from a instant large pH drop, but was still low pH) unbinds some stuff and potentially ammonia can instantly form from something to very high, dangerous levels for fish.
There was also some mention of oxidation, but clearly I have forgotten what was said and I have no clue what I am talking about, but maybe it will cause you to remember or consider something you may have overlooked in regards to low pH.
Also people mention large pH drops are deadly too fish, but you say yours are doing fine with large pH drops, so I don't know what exactly is going on, everyone else's test results (pH, GH, KH, co2 concentrations) seem to add up when comparing levels to how fish are behaving.

For reference, this stuff was talked about in threads when I was researching dangerous gas pockets under the substrate (a question I will ask about in the near future) in anaerobic and anoxic conditions. Someone had gas pockets they released when they disturbed the substrate and fish all died, so people were trying to figure out potential cause and mentioned the possibilities I just broadly mentioned, completely different topic, but low pH was mentioned. I have done similar in the past, but my fish didn't die, almost though, so I do believe there is potential for deadly gasses (I don't mean Hydrogen Sulfide or Methane gas, must be something else) to form under the substrate, just can't figure out what exactly (it wasn't debris being kicked into the water column causing spikes).

I don't know, just mentioning, maybe you can shed some chemistry light on that for me again haha

ehh, tried to find the threads I was talking about, but couldn't find at the moment, but I did run across two pages that I found interesting even though the chemistry is too advanced for my level of comprehension on the subject haha.
Not really on topic to this thread, but might be a interesting read for you since you can actually understand them

Last edited by WaterLife; 09-26-2015 at 09:42 AM. Reason: +
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post #3 of 14 (permalink) Old 09-26-2015, 10:42 AM
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You said you would like longer light hrs. If it's mostly for viewing think about this.
I had the light photo period different at first, but noticed as many have that the fish
got freaked out when the light came on while it is still dark inside, sun not up yet.
You can have more viewing time if you split the light "on hrs."
I changed the hrs to match my work hrs better. The light used to come on at 7:00A.M.
and go till 4:00P.M. to keep 9 hrs. Well I work nights and that had the light on when I came home, but not when I got up in the early P.M. about 5:00P.M.
I noticed that once I changed the time it came on till 8am the daylight was much better outside so there was some light in the tank when the light came on and the fish didn't freak near as much. The light goes off at 11:00A.M. and stays off till later in the P.M. so now I get to see the tank both when I come home and before I go to work but I still don't have long hrs of it total. Helps/w the algae. That was suggested as an additional/mild form of algae control, but gave me more viewing hrs without making the hrs longer.

The shortest distance between any two points is a straight the opposite direction...
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post #4 of 14 (permalink) Old 09-27-2015, 12:20 AM Thread Starter
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In a nut shell, ammonia is more toxic at higher pH and higher temperatures. So in this case, lower pH reduces probability of ammonia toxicity.
The degree to which ammonia forms the ammonium ion depends on the pH of the solution. If the pH is low, the equilibrium shifts to the right: more ammonia molecules are converted into ammonium ions. If the pH is high (the concentration of hydrogen ions is low), the equilibrium shifts to the left: the hydroxide ion abstracts a proton from the ammonium ion, generating ammonia.
So really, there are two ions, Ammonia (NH3) and Ammonium (NH4+). As pH lowers (more H+), ammonia (the more toxic form) gains an Hydrogen (H+) ion to form the less toxic ammonium. Notice ammonia has one Nitrogen (N) atom and three hydrogen (H3) atoms, and ammonium contains the extra hydrogen atom.

Some of the trace elements work in reverse to this, lower pH increases their toxicity.

The substrate I can't really comment on, but if I had to take a guess, I would say it was to deep, without enough roots delivering oxygen.

I'll share some more thoughts on CO2 at a later date.

@Raymond S.
I've tried the split period before, I think I prefer a constant period. Just personal preference. Thanks.

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Last edited by Audionut; 09-27-2015 at 01:48 AM. Reason: spelling
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post #5 of 14 (permalink) Old 10-08-2015, 05:07 AM Thread Starter
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Two weeks after tank move.

The cloudiness has cleared up. This tank is a good reminder of the importance of patience, which I seem to have little of these days.

I've setup the nutrient drips, with NPK, Mg, Rexolin APN trace mix, and DTPA Fe each in separate bottles. I control Ca and CO3 with shell grit in the tank. I plan on reducing TDS as far as possible while watching growth and algae. Hopefully I can spot the limiting nutrient which will make it easier to then dial back the other nutrients until I find their limit on growth, reducing TDS further. Since there's a constant replenishment of water and the major and minor ions, precipitate should be a non-issue, helping to further reduce TDS, while still maintaining sufficient available elements. Once I've found the lower limit, I'll probably start increasing TDS and correlating with growth. It only cost about $15 AU to set the nutrient drip system up, so that was a bonus, but fine control and consistency is somewhat lacking. When the drip rates change, they tend to change towards lean, which isn't such a bad thing while reducing TDS, but will probably start to be a larger issue as I try and even things out, or even start increasing levels. Constant fiddling has got things pretty consistent, but I'd happily trade money for the time if I had the spare cash laying around. Accuracy would increase also.

There's a couple of drop checkers in the tank. I'm trying to correlate some data regarding CO2 levels. I think I'm wasting my time here though. I'm trying to find the maths behind accurate CO2 concentration, but being maths dumb doesn't help. I've pushed the pH down 1.9 points from degassed state, and will continue pushing it down until I get worried or kill something. I've pushed it down 2.0 pH before I moved the tank, but I had nowhere near the balance and consistency I do now, got scared about the number and backed it off. This is basically just to gather data, as it appears that growth in the Java moss and Java ferns has slowed with continued increased CO2 levels. I'm not willing to make any judgements at this stage since I'm still changing to many things at one.

I've added some protection to the overflows in the form of free wire laying around, until I find a more elegant solution. I tend to think only the dumb things go down the overflow, which probably isn't such a bad thing (Darwin's law and all), but the snails can get jammed in the overflow system, which just causes headaches. I had some peppered corys which were really beautiful going along the front of the tank, but dumb, I was constantly fishing them out of the sump.

Some new plants in there (two days ago) which has added some variety, and I'm keen to get some red plants growing nicely. The last effort was a terrible failure.

Most of the fish are still juveniles, but there's a clear food chain developing. Male BN, Gourami, Tiger barbs, SAE, Tetras, Corys. The Tetras will school reasonably often (Rummynose are excellent), but the environment is pretty placid, and they tend to spend most of their time in safety. When I added the Tiger barbs, that really livened things up, I has some flow in there that the Tetras were used to and the Tiger barbs were to used to dead calm water. But by golly gosh did they try and annoy everything in the tank. They really got everything schooling. Things have settled down now, and the Tiger barbs are mainly opportunistic when a algae wafer goes in, and tend to only annoy each other.

They started annoying the Gourami, but she's obviously worked out she's the biggest fish in there. After spending a few days annoying the Tiger barbs, he appears to have exerted his dominance. There's a pretty nice balance in there between liveliness and problems. I'd like to have some more danger in there to keep the Tetras schooling, but I don't think I'll be able to in this sized tank. It's a case of either far to aggressive, or aggressive for a few days, at which point things settle down and everything lives happily together. I fed them some live mosquito larvae yesterday, which created some action. Keen to see if they display the same behavior at the next feed.

Originally Posted by WaterLife View Post
What size tank is the Discus tank?
Missed this question last time. As big as possible.
I'll worry about getting this tank where I want it first.

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Last edited by Audionut; 10-08-2015 at 10:40 PM. Reason: He is a she
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post #6 of 14 (permalink) Old 01-17-2016, 11:55 PM Thread Starter
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Time for an update.

Things are kicking along really nicely. (click for bigger).

Some notes:
Graphs are from the month of January.

Some of the spikes might look big, but that's only because I'm manually logging the data. The first drop in pH for instance, from 5.4 pH to 4.2 pH is over a span of three days.

ORP is not calibrated.

TDS meter was calibrated at 64ppm.

GH and KH test kits reliably measure 14% high. Current GH measures 47.6 ppm, which puts the more accurate result at 41 ppm.
To measure KH, I use a 90ml sample and divide the number of drop taken to change color by 18 (90ml / 5ml). This should bring resolution of each drop to (17.848 / 18) = 0.99 ppm. This worked really well when KH was above six ppm since there was a distinct color change. However, at this low level it is hard to determine accurate result (just like trying to measure low KH with a 5ml sample). One drop of the KH solution gives a distinct blue tinge, but it's difficult to tell the difference after that. I've tried using even larger water samples, but it appears that I've just hit the limit. With more water there's just to much water compared to KH solution, and it's even harder to judge color change.
To measure GH, I've been using a 30ml sample and dividing by 6 (30 / 5) giving a resolution of (17.848 / 6) = 3 ppm.

Current dosing is as such.

This is done via the following. The amounts listed below are the daily dose all in ppm.
CaMg(CO3)2		Ca=0.838	Mg=0.508	GH/KH=4.18	C=0.502
CaCO3			Ca=0.686	GH/KH=1.71	C=0.205
KHCO3			K=1.69		KH=2.166	C=0.5198	H=0.0436
NaHCO3			Na=0.00045	KH=0.00099	C=0.000238	H=0.0000199
CaCl2			Ca=0.0025	Cl=0.0045	GH=0.0064
KH2PO4			P=0.26		PO4=0.797	K=0.328		H=0.00846
K2SO4			K=0.3		S=0.1328	SO4=0.398
(NH4)2SO4		N=0.5		NH4=0.6499	S=0.2479	SO4=0.7428
CH4N2O			N=0.444		C=0.19		H=0.01598
Amgrow trace mix	Fe=0.0032	Mn=0.00158	B=0.0003	Zn=0.000257	Cu=0.000128	Mo=0.0000857	all EDTA chelated
ZnSO4			Zn=0.000102	S=0.00005	SO4=0.00015
MnSO4			Mn=0.00194	S=0.00125	SO4=0.00376
Na2B4O7*10H2O		B=0.00323	Na=0.003444
EDTA Fe 13%		Fe=0.01114
Citric acid		C=0.1393	H=0.0155
Some notes:
The initial target is/was 1/20th Hoagland solution.

Auto doser doses everything except CaMg(CO3)2 and CaCO3 every hour.
HCO3 sources are dosed at 10 past the hour.
PO4 is dosed 55 past the hour.
NH4+Urea+K2SO4 is dosed 40 past the hour.
Trace mix (everything else) is dosed 25 past the hour.

N has been lowered in an effort to keep NO3 levels within reason. My stem plants are really good N indicators. Lots of N (10ppm), nice big growth, little N, small growth. I'm trying to find that point where growth is nice and lush, and NO3 is low. I keep fairly consistent water parameters as can be seem via TDS graph. Things don't get a break on water change day (large 50% water change), so I need to balance NO3 effects on the fish. I'm pretty happy where things are now, growth is noticeably smaller on the stem plants then I would like, but NO3 seems reasonable. I will continue to further adjust things by trying to maintain N fixing bacteria.
Also note, the water volume is around 350 liters which contains 70+ fish and snails. I cannot even begin to ascertain their combined N output. I may try stopping N dosing in the future to try and determine fish load.

CaMg(CO3)2 and CaCO3 doses are best guesstimates. My only Ca++ source is coral sand. I was maintaining 10 ppm Ca++ measured by a calibrated test kit, but GH readings were up around 65 ppm with MgSO4 dosing that would result in a maximum CaCO3 equivalent of 9 ppm. 65 minus 14% error minus 9 = 47 ppm CaCO3 equivalent of Ca++. 47ppm CaCO3 equivalent Ca++ is 18.8 ppm. Clearly, something is wrong.

I've been reducing weekly dosing of MgSO4 dosing from 2.5 ppm Mg++ to around 1.5 ppm Mg++ for around 3 weeks, then completely stopped MgSO4 dosing eight days ago. I have not seen anything that resembles Mg deficiency. Subjectively, I would say things have improved since stopping MgSO4 dosing (minus a S deficiency that I'll describe late). So I've decided to make the somewhat logical conclusion that Serenity Aquatics Natural Aragonite coral sand contains Mg.

So I hit the maths like so.
47.6 ppm GH - 14% error = 41 ppm GH.
10 ppm Ca++ = 25 ppm CaCO3 equivalent.
41 ppm (GH) - 25 ppm (Ca++ contribution) = 16 ppm.
16 ppm CaCO3 equivalent Mg = 3.8 ppm Mg++.
I then found the dose of CaMg(CO3)2 that hit the expected Mg++ concentration, and made up the remainder of Ca++ with CaCO3. Seems logical.

K is higher then I would like simply trying to maintain alkalinity (KH). As can be seen via the dosing graph, there is somewhere near 56 ppm CaCO3 equivalent of HCO3 being dosed per week, and yet KH maintains around 2 ppm. I choose K to be in excess because I believe it is the lesser of the evils (Ca++/Mg++, Na+, K+). I most certainly don't want anymore Na in the system, and I'd rather keep Ca++/Mg++ levels clearly into the soft water category. Snails are doing fine, so Ca++ is also fine IMO.

In the pH graph above, the large downward spiral of pH towards the beginning is where I thought lower pH would equal higher CO2. It simply costs to much to maintain a very consistent CO2 injection system here (where I live). Also, I would rather try and generate CO2 naturally (just because), and whatever level I can generate naturally is probably right on the money. So I had the bright idea of adding way to much Citric Acid to my PO4 solution. The even smarter thing about the idea was that I had also run out of PO4, so I couldn't make a new solution.

HCO3 was being transformed to CO2 + H2O as can be seen by the dropping KH results, however I don't think CO2 levels approached anything near 30ppm for a number of reasons.
First, the shear number of free H+ ions increased dramatically which throws off any means of accurate CO2/KH/pH measurement. For this measurement to be accurate, pH can only be affected by CO2+KH. Here, not only was there an increase in free H+ ions from Citric Acid, but also the pH buffer has been lowered with the addition of what had now become H3PO4 (Citric acid + H2PO4).

However, my opinion regarding the CO2 levels in the tank are such. There clearly isn't the amount of dissolved CO2 as what I was generating with injected CO2. Plants no longer pearl. However, plant growth is still crazy quick. Plant growth doesn't work on a linear scale with increasing light or CO2 or nutrients. Doubling CO2 concentration would provide some increase in growth rate, but is it worth the negative affect on other life in the tank. FWIW, my RODI water is 5.4 pH and a 4 dKH solution is around 7.0 pH.

I was dosing lots of Fe, some 0.2 ppm per day. Based on the comments from @Marcel G, I figured I was probably adding excess amount of Fe. However, since I had been reducing MgSO4 dosing and that was my only source of S, reducing the Fe dosing uncovered the S deficiency. I was using only Urea for N, so I switched over to (NH4)2SO4 + urea. I've since added K2SO4 for some extra S, but what I should have done was just made my N dosing completely (NH4)2SO4. The K2SO4 is adding around 2.1 ppm of K per week, so that's 2.1 ppm of K I can shave off at a later date when I make a new solution bottle.

The last time I added additional Fe was 6 days ago (0.1 ppm DTPA Fe). I'm seeing what looks like Fe deficiency this morning and added 0.06 ppm Fe. Will need to monitor this, but it appears like 0.1 ppm EDTA Fe per week isn't sufficient for my system.

I'm currently under the impression that it's probably best to have the pH closer to 5.6 pH, to ensure all chemical species are best balanced with regards to solubility/precipitation. I'm not keen on adding anymore HCO3 sources, since I don't also want the increase in other elements (Ca++/Mg++ or Na+ or K+), the other option being to increase surface agitation, but naturally that will result in lower CO2 concentration which I'm not real keen on either. I'm tending to think that if I can increase pH (boost with something), and hence, reduce free H+, I might be able to get away with the same dosing to maintain pH at that higher level. But that's an experiment for another time.

Anyway, that's about it for now. I could continue but this post is already long enough. Besides, I'd rather answer any questions then continuing to rabble on about stuff.

Just to be clear, the idea is to only add whats needed, not just dump excess of everything in there based on liebig's law.

EDIT: Some further details.

I have two 2 foot T8's on a 12 hour and 20 minute light on, with a 4 foot double T5HO on a 10 hour and 20 minute light on. The tank was algae free to the point where old algae was also dying off. The T5 was on a 12 hour light on, and I just added the dual T8's. I started seeing algae in the hot spots, clearly the balance had been thrown off. So I reduced the lighting to the above, and things seem to be getting better balanced again.

I water change 15% per day, using a drip system that takes 5 hours to accomplish the task. Hence the bumps in the TDS graph. You can clearly see day to day in the TDS graph. The larger dips in TDS is where I've cleaned out the build up of organics in the sumps and replaced with RODI with only a little KHCO3.

I couldn't help myself, and have replaced the (NH4)2SO4 + Urea + K2SO4 solution for straight (NH4)2SO4. This has kept N as the same rate, increased S and reduced K.

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Last edited by Audionut; 01-18-2016 at 04:51 AM. Reason: add
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post #7 of 14 (permalink) Old 01-18-2016, 01:31 PM
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Hi Audionut,

if you allow I have several notes (with all the respect to your experiment):

- I would like to see some so-called "hard" plants in your tank to know how would they do.
- I don't think such a low pH is good for fish (nor for nitrifying microbes). I understand that they may seem fine, but I don't think it's good for their long-term health/condition. In aquaculture and water chemistry literature you may find more relevant data that explain why it may not be a good idea to keep fish under such a low pH. But maybe the fish species you have are well adapted for it.
- As I already stated, the ORP values seem extremely high to me, but it may not necessarily mean a bad thing. I see a difference between the measured value, and it's interpretation. The ORP is quite complicated stuff. PS: Are you sure your values are in ORPm, not ORPh?
- The alkalinity (KH) drop may be also due to the transformation (consumption) of HCO3 by plants. If they have not enough CO2, some of them may use HCO3 as their carbon source. If you are not adding CO2 gas into your tank, then probably you have just a "natural" level in your tank.
- Are you really sure your plants need 5 ppm PO4? Did you do any tests to verify this? I doubt they are able to uptake this amount, and even if they do, I doubt they really need it for growth.
- Also, did you tried to use less N in your tank? I know it's hard to compare two states if you can't see it simultaneously. I mean, it's hard to compare your tank under (say) 10 ppm NO3 vs. 30 ppm NO3, and compare the growth rates of your plants. I understand that 30 ppm NO3 may results in fastest growth rates, but I think that with 10 or 15 ppm you would hardly notice any substantial difference. Also, this way you could check if adding NH4 makes any real difference.
- Just a side note: It would be much better if you round the numbers in your table to one (or two) decimal places - at least for macroelements, as these decimal places you use right now are just a fiction anyway, and rounded numbers look more neat.
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post #8 of 14 (permalink) Old 01-19-2016, 01:00 AM Thread Starter
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Originally Posted by Marcel G View Post
- I don't think such a low pH is good for fish (nor for nitrifying microbes)......................................... ....................Also, did you tried to use less N in your tank? I know it's hard to compare two states if you can't see it simultaneously. I mean, it's hard to compare your tank under (say) 10 ppm NO3 vs. 30 ppm NO3, and compare the growth rates of your plants. I understand that 30 ppm NO3 may results in fastest growth rates, but I think that with 10 or 15 ppm you would hardly notice any substantial difference. Also, this way you could check if adding NH4 makes any real difference.
I would love to be able to better control nitrifying bacteria, as they serve no useful function in my system. We know that plants uptake NH4, they can also uptake NO3 but must transform this form of nitrogen back to NH4 for use.

In a fish only system, or high pH system, it is these bacteria we know that help to support life through the transformation of highly toxic NH3, or excess NH4 into far less toxic NO3. Very useful function.

But now consider my low pH system that allows some amount of elevated NH4 concentration. I'm dosing 0.93 ppm of N as NH4 per day (1.2 ppm NH4) into what should otherwise be (without plant uptake and nitrogen transformation) an accumulated concentration of 6.2 ppm N (8 ppm NH4). Do I need this level of N (NH4) for reasonable plant growth? I should think not.

The issue is, that not all of the N as NH4 is available to the plants, some of it is transformed by nitrifying bacteria into NO3, which then must be denitrified by the plants back into NH4, requiring energy to do so. Without nitrifying bacteria, I would have no loss of NH4 to NO3, and hence, I could add significantly less NH4 to maintain the highly available (low energy requirement for use) form of N. Oh, and of course, with no NO3 dosing or nitrification of NH4 > NO3, NO3 concentration would be 0 ppm. Efficiency.

Originally Posted by Audionut View Post
Some notes:......................................N has been lowered in an effort to keep NO3 levels within reason. My stem plants are really good N indicators. Lots of N (10ppm), nice big growth, little N, small growth. I'm trying to find that point where growth is nice and lush, and NO3 is low.
My N dosing has been as high as 2 ppm per day (NH4 + CH4N2O), and I can assure you that the affect on growth between that dosage and my current dosage (0.93 ppm N) is very noticeable, even without side by side comparison.

Here's the thing Marcel.......It wasn't the increased NO3 concentration that facilitated that increased growth of the stem plants. The NO3 being nothing more then a byproduct of an unwanted biological process. It's the increased availability of more efficient forms of N that is the interesting part. I facilitate this availability by destroying some part of the nitrifying bacteria colony. Give or take, NO3 concentration remains the same as lower doses of N, through the process of water changes and destruction of nitrifying bacteria, but plant growth increases significantly.

So you look at my N dosing and see NO3. But I only supply NO3 data to show what the resulting NO3 concentration would be if all of the N sources were transformed to NO3. Perhaps I should just remove this data for increased intelligibility.

Since some part of the learning process in this system also means the reduction of manual tasks to support it, the constant removal of nitrifying bacteria goes against this standard. So I need to find that balancing act between available N, for my own personal needs and desires regarding growth, and the concentration of an unwanted byproduct (NO3).

Originally Posted by Marcel G View Post
I understand that they may seem fine, but I don't think it's good for their long-term health/condition. In aquaculture and water chemistry literature you may find more relevant data that explain why it may not be a good idea to keep fish under such a low pH. But maybe the fish species you have are well adapted for it.
pH is simply an indicator, affected by numerous chemical species, and affecting numerous chemical species.

Is low pH the cause of long term health conditions because of increased CO2, or decreased alkalinity, or increased concentrations of available heavy metals, or decreased availability of other ions, or some combination. These are the questions I would be asking Marcel, rather then painting everything with the same low pH is bad brush.

Originally Posted by Marcel G View Post
The ORP is quite complicated stuff.
Indeed it is. Home are some of my general opinions regarding ORP.

ORP and pH are tightly related. A pH drop of one equals an increase in ORP of 58mv. So my corrected ORP value against neutral pH is closer to 600mv (in other words, all other things being equal, my ORP reading should be 600mv if pH was increased to 7.0pH). Still somewhat high I guess, but probably not so high to generate the OMG YOUR ORP IS SO *UCKING HIGH responses that I have been getting.

ORP is a indicator of the oxidizing and reducing agents in the water. Looking at some of the reducing agents, we see, Ca, Mg, Na, K, Cl, Cu, Li, Al, and compounds containing the H- ion. Some of these I already have in excess of unpolluted waters (K+), others I just don't want at all (Li, Al), and others again that I would have in concentrations equal to some natural waters (Ca, Mg, Na, Cl, Cu).

I don't want to increase any of these elements, and I find hard to believe that low pH waters found naturally without significant pollution contain high levels of these elements. Instead, I believe that low pH waters in nature that contain lower ORP values are directly related to the level of oxygen consuming microbes. Since oxygen is an oxidizer, lower levels of oxygen will shift the ORP balance to lower mv values, and high levels of microbes are needed to clean these waters.

So then the questions remain. Are these microbes a valuable commodity to my system in the same quantities as found in naturally low pH waters? And regardless of whether I have the same concentration of these microbes vs water volume as these water bodies, it really only boils down to the oxygen concentration. Do I really want to increase the organic matter of my system to increase microbe concentration, to reduce oxygen levels, just to hit some possibly misguided interpretation of optimal ORP level?

If I add things like Citric acid (C6H8O7), pH lowers, and you guessed it, ORP increases.

edit: Correcting ORP against the pH of seawater brings my ORP reading to around 530mv. Still somewhat high, yes. But seawater contains significant amounts of reducing agents (Ca/Mg/Na/Cl).

Originally Posted by Marcel G View Post
PS: Are you sure your values are in ORPm, not ORPh?
The meter states it measures mv +/-. I can't say anything further then that.

Originally Posted by Marcel G View Post
- The alkalinity (KH) drop may be also due to the transformation (consumption) of HCO3 by plants. If they have not enough CO2, some of them may use HCO3 as their carbon source. If you are not adding CO2 gas into your tank, then probably you have just a "natural" level in your tank.
Highly unlikely. It is my understanding that plants will only begin to source C from HCO3 when CO2 concentration is significantly limited.

I absolutely have a natural level of CO2 in my tank. Natural levels of CO2 vary considerably.
I don't claim to have 30 + ppm of CO2, but I am very confident I have a CO2 concentration in excess of equilibrium with the atmosphere, which I might add, arguably more importantly then the concentration in itself (30 ppm vs 10ppm), is the fact that the concentration is very consistent.

edit: How confident am I that CO2 concentration in the water is above equilibrium with the atmosphere? Simple. I increase surface agitation and pH rises. If the water was in equilibrium, and increase in surface agitation would have no affect on pH.

In the following image I have marked the KH readings against pH.

(H+) + (HCO3) = H2CO3. The addition of H+ has increased the concentration of H2CO3 causing a reduction of HCO3 and pH. I suspect CO2 concentration has remained somewhat unchanged in this situation since the HCO3 concentration decreased relative to the increase in H2CO3 and is reflected by pH. Here, pH has dropped relative to decreasing HCO3 concentration.

If I want to increase CO2 production in this system, I'm pretty sure I need to have the same increase in H+, without the reduction in HCO3. In this situation the system would be generating excess C. Here, H2CO3 concentration would increase, HCO3 concentration would remain stable, but pH would change reflecting the increase in CO2, rather then the decrease in KH.

But, (H)CO3 only bonds with so many cations, and I have the desired concentrations of cations already in the water. I have some bending and warping of plant leaves that I'm pretty sure is related to Ca++/Mg++/K+ or some ratio of concentration between them. CaMg(CO3)2 is probably the best method of increasing KH, since I net two CO3 anions for every Ca and Mg cation, plus, CO3 is really good KH buffer being able to accept two H+ ions.

I think I will proceed by increasing KHCO3 dosing though, since this is very easy and I can accurately measure KHCO3 dosage. This will help to increase HCO3, plus increase K relative to Ca and Mg. I will note results on plant growth. If increased K doesn't fix the problem, I will then reduce KHCO3 dosing, and try an increase of CaMg(CO3)2 instead. In either case, hopefully one of the solutions will work, since increased HCO3 should also facilitate increased CO2.

Something I was pondering last night. When we inject CO2 into the water, some of this CO2 combines with free H2O molecules to form H2CO3. A decrease in free H2O molecules for an increase in Carbonic acid. Where we generate CO2 with the transformation of HCO3, we reduce HCO3 for an increase in CO2 and H2O. Which one do you think is the preferred method?

Originally Posted by Marcel G View Post
- Are you really sure your plants need 5 ppm PO4? Did you do any tests to verify this? I doubt they are able to uptake this amount, and even if they do, I doubt they really need it for growth.
Mainly because PO4 < 5 ppm = GSA.

But also because 1/20th Hoagland solution = 1.55 ppm P which equates to 4.75 ppm PO4.

Did you do any tests to verify this concentration of PO4 is detrimental? I have absolutely no concerns regarding this concentration of P. If this ratio of P vs other ions is satisfactory for a solution that is supposedly used by scientists world-wide, then who am I to argue. Mark my words though, while I am very comfortable with this concentration of P, when I am very comfortable with the concentrations of the other ions in my water, P will make the short list of ions to try and reduce to observe effects.

Originally Posted by Marcel G View Post
- Just a side note: It would be much better if you round the numbers in your table to one (or two) decimal places - at least for macroelements, as these decimal places you use right now are just a fiction anyway, and rounded numbers look more neat.
True. I'll have a look at figuring out how to make the spreadsheet automatically round off. Right now everything is automatically generated based on the calculated concentrations of ions against dosages.

The spreadsheet is here if you're interested. But I've slowly been adding to it for some time, so it's a mess and probably not easy to understand.

Thanks for taking your time to respond.

Feel free to edit.

Last edited by Audionut; 01-19-2016 at 01:36 AM. Reason: Some ORP and CO2 stuff.
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post #9 of 14 (permalink) Old 01-19-2016, 06:49 AM
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Low pH effect on fish

Article: The physiology of fish at low pH: the zebrafish as a model system
DOI: 10.1242/jeb.091603
URL: The physiology of fish at low pH: the zebrafish as a model system | Journal of Experimental Biology

"Acid exposure can affect the gill in numerous ways, such as by increasing the number and turnover of ion-transporting cells (ionocytes), elevating mucus production and recruiting leukocytes. Breakdown of gill structure and suffocation caused by mucus accumulation may also occur in fish exposed to extreme acidic water (pH 2.0–3.5). At about pH 4.0–4.5, however, the primary effects of acid exposure on most fish species that have been examined are inhibition of active Na+ uptake coupled with increased rates of passive Na+ losses, leading to a decrease in plasma Na+ level."

"Probably the most extensively studied group of acid-tolerant species of fish are found in the Rio Negro of the Amazon River system. While Rio Negro water chemistry is extremely harsh (pH is around 4.5–5.1; Na+ and Ca2+ levels are ~10 and ~5 μmol/l, respectively), ~1000 species of fish are estimated to be distributed in these waters. Previous research identified two major strategies for fish to defend Na+ homeostasis in such an environment: (1) the functioning of a high-capacity, high-affinity Na+ uptake mechanism that is largely insensitive to acid challenge, and (2) an insensitivity of Na+ efflux to acid exposure."

"A complicating factor associated with the acidification of water is increased leaching of toxic trace elements from the soil and rock into the water; the increased concentrations of toxic metals may impose additional challenges on fish. In particular, the elevation of Al3+ concentrations in acidified lakes and streams maybe an important factor contributing to fish mortality."

[My note: 5 μmol/l Ca++ = 0.2 ppm; 10 μmol/l Na+ = 0.23 ppm]

After I did some brief research on "low pH effect on freshwater fish", I have to admit that you are probably right about asserting that such a low pH of yours (4.1 to 5.7) have little negative impact on most tropical fish (see some of the article citations above).

Your NH4 supply system is also very interesting under this low pH level (and make sense to me).
The only downside so far I see in possible metal toxicity issues, as under low pH levels heavy metals may leach from the soil and rock into the water, so in some environments this may become a problem.

I don't have enough understanding of the ORP so I can't comment on this (although I have some opinions). But in case your ORP meter is showing ORPh values, your ORPm values would be by about 200 mV lower (so your +600 mV would mean +400 mV), thus perfectly corresponding to most measurements of other hobbyists. You may try to contact the ORP meter manufacturer to check this out (in case you are interested). But in my opinion such a scenario is not common (I never heard of any ORP meter with factory settings set to measure ORPh values instead of ORPm values).
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Last edited by 58417; 01-19-2016 at 07:08 AM. Reason: citation
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post #10 of 14 (permalink) Old 01-20-2016, 12:40 AM Thread Starter
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Keeping pH around 5.5 should keep the chemical species such as Aluminum, Uranium, Chromium and Lead, well outside of their soluble predominance, while pushing Manganese, Boron, Zinc, Copper, Cobalt and Molybdenum into soluble predominance, and helping to push Fe towards soluble predominance.

Thanks for the link, a good read.

Feel free to edit.
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post #11 of 14 (permalink) Old 01-20-2016, 02:29 PM
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You tank has really taken off and looks great. Keep us updated.
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post #12 of 14 (permalink) Old 01-30-2016, 02:19 AM Thread Starter
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For anyone who was following the thread, I was suffering what appeared to be a precipitation issue with my trace mix. I had significantly reduced trace dosing, including stopping all trace dosing.

The issue was no longer present.

Slowly I had been increasing the trace dosing reaching the following weekly dosage. The ratios of this solution were determined by some averaging of various trace solution mixes.

Fe	0.1515
Mn	0.0231
B	0.0058
Zn	0.0088
Cu	0.0018
Mo	0.0012
There were no issues that could be seen. Around four days after this I decided that I should try targeting a Hoagland solution ratio again.

Fe	0.01
Mn	0.025
B	0.025
Zn	0.0025
Cu	0.001
Mo	0.0005
Three days after this, the precipitation issue appeared again. I've since switched back to the old solution mix and the precipitation has disappeared. A quick look at the differences of the solutions shows the ratio of the nutrients between between the Hoagland mix and my custom mix is as follows. This is the ratio of Hoagland against my mix.

Fe	0.066
Mn	1.082
B	4.310
Zn	0.284
Cu	0.555
Mo	0.416
In other words, in the Hoagland solution mix, Fe, Zn, Cu and Mo were dosed at much lower concentrations, Mn around the same concentration and B around 4.3 times as concentrated. A betting man would probably lay his money on B as being the cause.

The revert back to the original solution mix was eight days ago. I've been seeing some Fe type deficiency symptoms which a little dose of Fe seems to be somewhat resolving. However, four days ago I performed a substantial trimming of the stem plants (I had been lazy and letting them grow wild). Since this trim back, the deficiency symptoms (loss of color in new growth) has become significant. Some of the new growth is almost white. I suspect this to be trace deficieny (immobile nutrient), but not necessarily Fe. In fact, probably not Fe since I've been dosing a little extra DTPA Fe and have registered some Fe with a test kit this morning.

With a little refinement of the trace mix, and a little boost in dosage I am currently at this weekly solution.

Fe	0.2021
Mn	0.0308
B	0.0078
Zn	0.0118
Cu	0.0035
Mo	0.0016
Some color has returned to the new growth, although I plan on increasing the dosage a little higher.

The other issue I've been working on is the swings in TDS from the hourly dosing and daily water changing. Previously, I was seeing increases in TDS of approximately 12-13 ppm between stopping water change and starting next water change (around 19 hours of time), and TDS decreases of around 10 ppm during the time it takes to do the 15% water change (around 5 hours).

I make my solution mixes to target 24 ml dosage per day, dosed hourly (1 ml / hour). If I needed to increase dosing, I would just randomly increase some of the hourly doses to 2 ml, and if I needed to decrease dosing, I would just randomly stop some of the hourly doses. Then it made sense that I should probably be increasing the dosing during water change hours, and decreasing the dosing during the off hours.

Currently, this has reduced the TDS swings both off hours and during water change hours to around six ppm, and looks to have reduced the overall accumulation of nutrients in the water, since more of the nutrients would be lost during water change.

The large dip in TDS at the end of the graph is where we lost power during a storm yesterday, but I continued with the water change. Some of the resulting increase in TDS from this point was the result of the sump once again cycling.

My current dosing regime is as such. Each number represents a one ml dose.

I've been following a strict water on and water off routine to help observe trends. Water on at 10:30am and water off at 3:30pm.

@Marcel G, I've been slowly reducing the N dosing and currently have it down to 4.5 ppm NH4 / week (15.6 ppm NO3 equivalent). I was under the impression that the growth hadn't reduced in size that much until the other half commented on the lack of size to the stem plants recently. Heh, lol. You're notes, observations, concerns et al seem to have struck a cord with me though, since I feel like persisting in the reduction of N.

I also seem to have found balance in the tank again, with a lack of GSA after the significant increase in light. Still little bits of GSA in the heavily lit areas, but growth is very much slowing. So I have begun P reduction.

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Last edited by Audionut; 01-30-2016 at 04:41 AM. Reason: add dosing regime image
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post #13 of 14 (permalink) Old 02-05-2016, 01:06 AM Thread Starter
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Some interesting observations.

  1. Last recorded data at night
  2. Lights on
  3. Water on
  4. Water off
  5. Lights off

The dosing schedule.

Each number represents a milliliter dose. So the number 5 represents 5ml as being dosed.

The dosage amounts.

The first column is listed as the hourly dose from the days when I was dosing everything hourly, but what it really represents is the dose from 1ml of the nutrient solution.

For clarity, the first light comes on at 09:50 am, and the last light turns off at 10:00 pm. In the area noted with the arrows in the pH chart above, RODI water was turned on at 10:39 am and turned off at 3:33 pm. So the area between 1 and 2 in the graph represents the pH change between lights off the previous night, and light on the next day. Between 3 and 4 being the time that RODI water is being dripped into the system, and between 4 and 5 bring the time between water off and lights off.

There are some small variations that have been the result of circumstances not allowing the exact turn on and turn off of water at the prescribed times, but a definite pattern has emerged.

  • Whatever the rate of consumption of CO2 by the plants, the effect is less on pH then that of the other chemical processes.

As plants consume CO2 during photosynthesis, we should expect to see pH rise.

  • Within the bounds of accuracy of the test kit, and my testing, KH does not change.

I use a 90ml sample of tank water which increases the resolution of the test kit to around 1 ppm KH. I've measured KH before the addition of RODI water, and after the last large dose of HCO3. Since KH does not change (or at least, does not change significantly), the effect on pH is not a result of changing KH.
If KH was a contributing factor in the effect on pH, we should expect to see a reduced KH value the following morning after the reduction of pH, and also, we would not expect to see pH climb.

So this leaves two functions that can affect pH. Changing CO2, or changing of the concentration of other acid sources. In my Trace and NH4 solution mixes, I also added a small amount of Citric Acid.

Initial conclusion:
The addition of RODI water reduces KH concentration, however, this is off-set by the dosing of HCO3 during this addition of RODI water. There will be small fluctuations in KH during this time, however they do not account for the large effect on pH after the period when RODI + KH addition to the tank occurs.

If the effect on pH was a sole function of the citric acid, we should expect to see the continued reduction of pH during the night as this citric acid continues to be dosed.

Based on the above, I think I can reasonably come to the conclusion that the effect on pH is significantly contributed to changing CO2 concentration. A time line can be painted like so.
  • Addition of HCO3 + H+
  • Increased CO2 concentration from the above, with the effect on pH being offset by increasing HCO3 addition
  • The stoppage of HCO3 dosing resulting in the increasing CO2 concentration being reflected by pH
  • The eventual decline in increased CO2 production being reflected by the increase in pH. CO2 being offgased at a faster rate then CO2 production

Confounding factors:
What role does the buffering capabilities of PO4 and NH4 have on pH?
How fast or slow are the various chemical reactions?
What else is happening that I am unaware of?

With these confounding factors, I still feel comfortable coming to the conclusion that the significantly contributing factor towards pH change is CO2 concentration. However, a greater understanding of the confounding factors would lead to a better understanding of just how large the effect on pH is from CO2, and how large the affect is from the other factors.

Also note: PO4 plays (almost) no role on KH test kits in my system.

The pH of my system (5.5 pH) means that the predominant species of PO4 is H2PO4, and KH test kits do not titrate samples below pH around 4.5 pH. In other words, KH test kits do not shift the PO4 species in my tank.

Next steps:
Adjust the water change and dosing hours to move the point of expected highest CO2 concentration (lowest measured pH) more inline with expected peak plant photosynthesis. Currently, the lowest measured pH point is occurring around the time of lights off.
Better understand the things I don't fully understand.

Feel free to edit.

Last edited by Audionut; 02-05-2016 at 01:26 AM. Reason: remove unnecessary
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post #14 of 14 (permalink) Old 02-05-2016, 02:55 AM
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Subscribed! Keep it up. I enjoy learning the science behind this.
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