Question from a chemist about water changes - Page 3 - The Planted Tank Forum
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post #31 of 45 (permalink) Old 10-14-2020, 12:49 AM
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Organic molecules are important to the formation of CaCO3 in many organisms. "Organics" can bind with the metals in our tanks, acting as chelators (think: humic/fulvic acids), and may make them easier to consume and simultaneously reduce toxicity.
While FA can bind heavy metals and is suggested to be added in Aquaculture to help with fish health as it removes heavy metals from fish, it isn't produce by fish or contained in their waste unless it was added to their food.


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post #32 of 45 (permalink) Old 10-14-2020, 01:22 AM
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While FA can bind heavy metals and is suggested to be added in Aquaculture to help with fish health as it removes heavy metals from fish, it isn't produce by fish or contained in their waste unless it was added to their food.
Yes, fish food, just as many organics are transferred through the fish. They are also deeper within many of the fish food ingredients without being listed separately. I believe they also develop from decaying plant matter and decaying microbes. Certain substrates will also contain them. However, there is a great deal of mystery around them, but they do seem to be critical to plants. Interestingly, there are supplements that contain fulvic acids, but there is nothing to say that natural activity doesn't already provide plenty.
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post #33 of 45 (permalink) Old 10-14-2020, 04:45 AM Thread Starter
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But if all you have is a 2inch oscar(???) in a 120G there shouldn't be a lot of waste or feeding until it grows up.
Different tanks. One 2" oscar by himself in a 55-gallon, one mature oscar by himself in a 120-gallon.

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TDS of your tank water is 1000 or your source water? (Also what is the range of your TDS meter as a lot of the hobbyist ones can't go past 1000).
I believe the current model from HM Digital (mine is a bit older, but looks the same) would be the TDS-4, which reads 0-1000 at a resolution of 1 ppm, and 1000 to 9990 at a resolution of 10 ppm. I am a sad, awful chemist for not calibrating it, but I figure so long as I know my RO unit is giving me a certain concentration and the current concentration is much higher than that, I'm making progress anyway.

Tapwater this evening came out at 654 ppm, TDS from the under-the-sink RO came in at 50-something, the wall-mounted one outside has read as low as 24 ppm recently.

As for the ~1000ppm on the 55-gallon tank, I don't always monitor the TDS out of the tap. Back when I had a job involving a very large RO unit and a very large tank for a decent-sized hydroponics research greenhouse, we would routinely check our source water; normally it was 500 to 1000, although others had reported spikes as high as 1500. Phoenix metro gets its water from canals (CAP water from the Grand Canyon), subsurface water from wells around the city, and Salt River water from the impoundments there. It is sourced based on availability and demand, I suppose, by hydrologists with a lot more qualifications than I will ever have. So I doubt that ~650ppm tap water became ~1000ppm tank water from evaporation- probably just some hard water days on refills. That tank loses very little from evap. (SEE EDIT BELOW)

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The list of "organics" is plentiful. There are amino acids of various types, proteins, glycoproteins, sugars, and others. Anything with carbon and hydrogen is an organic (except bicarbonate and carbonic acid).

Assuming that the many known and unknown "organics" are bad may be wrong. Many of these may be useful in providing energy sources for various life forms in our tanks (bacteria being just one example).
It has been my experience from tissue culture and bioreactors that carbohydrates quickly become food for fungi, slightly less swiftly for bacteria. Proteins- or at least some of the component amino acids- are quite good as plant nutrients, at least in axenic culture: see also Malmgren's work with Soluvit and Vamin, which cracked the question of how to get nitrogen to plants without giving them ammonium or nitrate.

EDIT: I realized why the ppms were so high on the 55-gallon tank. A month or two ago, I tried to move the pH with vinegar. The water here has ridiculous buffering to it, it didn't budge. I added... quite a bit.

Last edited by osp001; 10-14-2020 at 06:50 AM. Reason: D'OH
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post #34 of 45 (permalink) Old 10-14-2020, 10:28 PM
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Originally Posted by Deanna View Post
The list of "organics" is plentiful. There are amino acids of various types, proteins, glycoproteins, sugars, and others. Anything with carbon and hydrogen is an organic (except bicarbonate and carbonic acid).

Assuming that the many known and unknown "organics" are bad may be wrong. Many of these may be useful in providing energy sources for various life forms in our tanks (bacteria being just one example). Organic molecules are important to the formation of CaCO3 in many organisms. "Organics" can bind with the metals in our tanks, acting as chelators (think: humic/fulvic acids), and may make them easier to consume and simultaneously reduce toxicity.

So, before trying to reduce the many "organics" whose processes we do not fully understand, we may want to be careful about what we ask for, as we may not like what we get in doing it. Unfortunately, these multitudes of "organics", and their impact, simply have not been studied well in aquariums. There is good and bad to all of this, but is the balance a neutral effect? If so, there is no need to worry about them accumulating, if the known dangerous/undesirable results of the organic processes are controlled.
Excellent post

You might be interested in COD Chemical oxygen demand test kit. It indirectly reads concentration of organic compounds in water. Hanna and also ADA sells one, here. ADA says

COD primarily reacts with organic materials in the water and indicates the degree of water deterioration. A high COD level could mean that the performance of your filters is declining, you have too many fish, or you are not changing your water enough. If the measured level of COD is too high, you should threat your water by changing it or some other appropriate method.

mg/L or ppm

<4
Normal water quality

6
Indicates considerable amount of organic material. Your water is dirty. You should change your water.

>8
Indicates high concentration of organic material. Water is serious condition with the growth of algae. You must urgently change more than half of your water.



Organic compounds degrade sooner or later, it’s all about balance. If you had 120 gallon aquarium with healthy growing plants and one Guppy fish you would never have any high organic issue in thousand years. It means that the rate of organic matter accumulation must be lower than the rate of organic matter degradation in order to keep the water healthy.
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post #35 of 45 (permalink) Old 10-15-2020, 02:09 AM
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Excellent post

You might be interested in COD Chemical oxygen demand test kit. It indirectly reads concentration of organic compounds in water. Hanna and also ADA sells one, here. ADA says

COD primarily reacts with organic materials in the water and indicates the degree of water deterioration. A high COD level could mean that the performance of your filters is declining, you have too many fish, or you are not changing your water enough. If the measured level of COD is too high, you should threat your water by changing it or some other appropriate method.

mg/L or ppm

<4
Normal water quality

6
Indicates considerable amount of organic material. Your water is dirty. You should change your water.

>8
Indicates high concentration of organic material. Water is serious condition with the growth of algae. You must urgently change more than half of your water.



Organic compounds degrade sooner or later, it’s all about balance. If you had 120 gallon aquarium with healthy growing plants and one Guppy fish you would never have any high organic issue in thousand years. It means that the rate of organic matter accumulation must be lower than the rate of organic matter degradation in order to keep the water healthy.
You would need to use the 'accurate' ADA one unless of course you have an $800 spare benchtop photometer lieing around to measure those hanna vials.


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post #36 of 45 (permalink) Old 10-15-2020, 02:21 AM
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Originally Posted by Deanna View Post
Yes, fish food, just as many organics are transferred through the fish. They are also deeper within many of the fish food ingredients without being listed separately. I believe they also develop from decaying plant matter and decaying microbes. Certain substrates will also contain them. However, there is a great deal of mystery around them, but they do seem to be critical to plants. Interestingly, there are supplements that contain fulvic acids, but there is nothing to say that natural activity doesn't already provide plenty.
Not to my knowledge, Fulvic Acid in Aquaculture can be used as a supplement/additive to prevent heavy metal toxicity and to promote healthier immune systems in fauna, and as a prophylaxis in fish or shrimp farms but nowhere have I read it is available in fish food in appreciable quantities unless supplemented.
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post #37 of 45 (permalink) Old 10-15-2020, 10:52 AM
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The problem with taking a measurement to determine if a water change is necessary is that it's reactive. The problem has already presented itself and it's effects felt either in terms of algae and/or fish health.

The best thing about water changes is that if anything they are proactive, preventive even if no issues are present. It's impossible to know what threshold each tank has before a problem starts. Doing regular water changes can only have a positive effect as long as the dosing is there.

The hobby is wide and certain setups can't be "balanced" without water changes. Not every hi-tech tank has wall to wall plants. Many have mostly hardscape and or are thinly planted and might still need good light to grow carpets. As you go up the aesthetic scale the more important water changes are as they provide you the freedom to do what you want within the glass box, not just throw in fast growing stems to balance things out. There's a large difference between an unlimited high-tech tank and a very limited Walstad one.


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post #38 of 45 (permalink) Old 10-15-2020, 01:26 PM
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You might be interested in COD Chemical oxygen demand test kit.
Thanks for the COD testing kits. Looks like the Hanna is designed for commercial/lab use, but the ADA looks more like hobby grade. I’d like to try it (although I’m not that concerned about my organics), but, like many ADA products, it doesn’t seem to be available in North America and I can’t read the languages of the websites in the countries where it does seem to be available.

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Not to my knowledge, Fulvic Acid in Aquaculture can be used as a supplement/additive to prevent heavy metal toxicity and to promote healthier immune systems in fauna, and as a prophylaxis in fish or shrimp farms but nowhere have I read it is available in fish food in appreciable quantities unless supplemented.
You may be right. Without re-doing the searching I did years ago, I can’t offer any countervailing support. My memory tells me that the likes of spirulina and chlorella in our fish foods do result in these acids either through digestion or decay in the substrate (who knows what the product of my many snails is). It does bring up the broader topic of the beneficial nature of the organic stream, though.

This searching was done when I was considering adding humic supplements to benefit both plants and animals. I didn’t want the tea-type appearance from things such as peat or catappa/Indian almond leaves, and who knows what the critical mass of these things are and how to determine if you even reach it. However, when researching the issue, it became clear that our tanks are probably supplying all of this in sufficient quantities (perhaps not enough for good breeding) and that using a proxy for excesses, such as TDS, would help prevent problems by indicating the need for a w/c.

Many reputable companies are now making these additives, but is it snake oil? I haven’t seen any credible testimony either way. We know these organics are there, but we don’t know the significance of the role they play, if any. We do tend to assume that they are uniformly bad and must be removed.

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The problem with taking a measurement to determine if a water change is necessary is that it's reactive. The problem has already presented itself and it's effects felt either in terms of algae and/or fish health.
I'm not sure that this is a given. Wouldn't we adjust our w/c threshold if we set a TDS indicator point that is too high? As in my statement about peat or catappa/Indian almond leaves, we don't know what the optimal time to do a w/c is (we have no useful measurements to judge). We end up believing that we must do it after a certain period of time, based upon our observations of changes in our tanks. If our parameters in a tank change, does this change the needed frequency of a w/c (rhetorical question)? Maybe this COD test would improve upon the TDS approach.
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post #39 of 45 (permalink) Old 10-15-2020, 02:08 PM
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I'm not sure that this is a given. Wouldn't we adjust our w/c threshold if we set a TDS indicator point that is too high? As in my statement about peat or catappa/Indian almond leaves, we don't know what the optimal time to do a w/c is (we have no useful measurements to judge). We end up believing that we must do it after a certain period of time, based upon our observations of changes in our tanks. If our parameters in a tank change, does this change the needed frequency of a w/c (rhetorical question)? Maybe this COD test would improve upon the TDS approach.
What's too high? The point I'm making is every tank is different and would be impossible to determine what TDS reading is good for each tank. Even if you had a good reading, if TDS prompts a water change the process has already stated in terms of algae, etc.

I've tracked alot of data on "ADA" tanks, and COD ranges from 2 to 8 mg/l and are spotless. So how do you judge what's within the threshold of each tank. Being proactive is the best approach before a problem starts.
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post #40 of 45 (permalink) Old 10-15-2020, 02:17 PM
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What's too high? The point I'm making is every tank is different and would be impossible to determine what TDS reading is good for each tank. Even if you had a good reading, if TDS prompts a water change the process has already stated in terms of algae, etc.

I've tracked alot of data on "ADA" tanks, and COD ranges from 2 to 8 mg/l and are spotless. So how do you judge what's within the threshold of each tank. Being proactive is the best approach before a problem starts.
I think we are making the exact same point: it is impossible to determine when the exact optimal time is to make a water change. Some do it based upon observations about changes in tanks, having learned to do it before a negative change occurs. Some do it by observing at what TDS point a negative change occurs and then do w/c's before TDS reaches that point. Both processes are based upon observations. ADA has done the same thing, but it seems specific to dissolved organics and they have described the COD thresholds to use based upon their observations. Being proactive about a w/c means that you have determined, for your tank, the time to do a water change because you've gone too far, before doing it, in the past.
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post #41 of 45 (permalink) Old 10-15-2020, 04:19 PM
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I will post the ADA COD instructions again because the way I understand it is ADA is encouraging aquarists to do everything they can, other than water changes, to keep organic compounds under control. First priority is given to filtration efficiency. Second is to reconsider the fish load, which implies to the balance between the fish load and the ability of the system to remove the organic compounds such as filtration size and plant mass. They are navigating aquarists towards more naturally sustainable setups where water change is the last remedy.

COD (Chemical Oxygen Demand) primarily reacts with organic materials in the water and indicates the degree of water deterioration. A high COD level could mean that the performance of your filters is declining, you have too many fish, or you are not changing your water enough. If the measured level of COD is too high, you should threat your water by changing it or some other appropriate method.

The closing sentence, “If the measured level of COD is still too high, you should threat your water by changing it or some other appropriate method.”, indicates that water change is not the only technique lowering organic matter.
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post #42 of 45 (permalink) Old 10-15-2020, 05:09 PM
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We end up believing that we must do it after a certain period of time, based upon our observations of changes in our tanks. If our parameters in a tank change, does this change the needed frequency of a w/c (rhetorical question)? Maybe this COD test would improve upon the TDS approach.
Not sure its the same thing. Preventive/Proactive is you do it before there's an indicator of a problem, like a flu shot.



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post #43 of 45 (permalink) Old 10-15-2020, 07:06 PM
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Not sure its the same thing. Preventive/Proactive is you do it before there's an indicator of a problem, like a flu shot. '
I think it is the same thing. You - proactively - have found that changing your water, e.g.; every 7 days, prevents negative things happening based upon your experience that waiting longer causes such problems. Others - proactively - have found that changing their water, e.g.; whenever TDS rises x% higher than a reset level, prevents negative things happening based upon their experience that waiting longer causes such problems. Both have a safe trigger for action and both are proactive.
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post #44 of 45 (permalink) Old 10-16-2020, 09:19 PM
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.... albeit in a different context (plant tissue culture), and I'm a chemist by training.
Sorry to hijack your thread for a second, but as it happens I asked on another part of the forum HERE is anyone else did their own plant tissue culture. If you've done any, maybe we can expand that thread a little.
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post #45 of 45 (permalink) Old 10-19-2020, 02:16 AM Thread Starter
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You would need to use the 'accurate' ADA one unless of course you have an $800 spare benchtop photometer lieing around to measure those hanna vials.

Seems one type of ADA kit uses dichromate, another boasts it is "mercury-free," which suggests disposal is going to be a nuisance with some of these.


FWIW, the ol' B&L Spec 20 analog spectrophotometers run about $50-100 on eBay. Been a while since I've gone through Standard Methods..., so maybe I'll fish up a method that doesn't have heavy metals disposal problems, see if it runs smooth on a Spec 20.
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