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Zorfox 04-24-2013 10:42 PM

Nutrient uptake ratios...
I have a 10g which I started two months ago. It has two 21w CFLs, pressurized CO2 @39ppm. It has grown to heavily planted. I've been dosing EI with 50% WC weekly.

My plan was to use the plants I had for cycling then rescape. But since I will be moving in 1-2 months I decided to let jungle grow until the move.

Yesterday I tested the water because I started to see some hair algae.
PH = 6.4
KH = 4dh
GH = 3dh
PO4 = 1ppm
Ammonia, nitrites 0
Nitrate = 0!

My kno3 solution raises the NO3 to 3.2ppm with each dose. I double dosed yesterday which brought it up to about 6-7ppm. Today nitrates are 0. Phosphate is about 2 after another KH2PO4 dose. I find it hard to believe the plants are uptaking 6ppm of NO3 per day. The kit is calibrated btw.

So my question is. Since the nitrate and phosphate uptake is obviously not in sync how do I know what plantex CSM + B to dose without an iron kit. Should I increase that by 1/3 or so? I have no idea where I am and would rather not wait for deficiecy problems.

Is there a general ratio for the three in regards to uptake I could use to make an educated guess?

HD Blazingwolf 04-24-2013 10:49 PM

if u have significant bio mass, and its severely in need of nitrates. it could theoretically absorb that much,

dose again and see what happens :)
it is also possible that ur substrate is abosrbing it through cation exchange

Zorfox 04-24-2013 11:02 PM


Originally Posted by HD Blazingwolf (Post 3212793)
it is also possible that ur substrate is abosrbing it through cation exchange

I didn't consider that possibility. Good point.

I am now left with guessing an appropriate trace dose. Since the uptake of each nutrient is non linear. Any reason why too much trace would be detrimental? Maybe increasing it by 30% or so. I really don't trust iron tests anyway.

PS I have never heard a 6ppm/day uptake of NO3, guess I need to look around more.

plantbrain 04-25-2013 06:11 AM

I tend to dose 15 ppm 2x a week of KNO3. Rarely 3x.

This seems good enough for most every plant species I've ever encountered, which is perhaps 400 species or so at this point.

If you look at a basic uptake and nutrient concentration graph:

EI targets the D range. A rich sediment like ADA AS, at least for the 1st few months, MTS etc, will do this as well.

By good observation, you can target the C range and slowly reduce and watch the plant's response.

Older methods used PO4 limitation to produce A and B ranges, which caused greatly reduced growth and also, less CO2 demand because plants were far more limited by PO4 or some other nutrient than CO2. Thus when they added the PO4 or the limiting nutrient, they then would have CO2 limitation, which tends to lead to algae, thus a myth is born. :icon_mad:

Hair algae seems more due to CO2 than anything else or plants growing and blocking the current. GHA tends to be near the current areas on the plants that block the current or are in the path of the current. This is also true in streams and rivers.

Also, do not assume the CO2 is 39 ppm, it might not be since the KH might be less than you think it really is. While we like to think it's all bicarb, sometimes it is not depending on the tap water.

Algae and plant health are better test kits, if not the best test kits. I'd focu there, provide ample nutrient, then mess with the CO2 mostly, and then good horti/aquaculture from there.

Zorfox 04-25-2013 05:37 PM

Thanks guys. I'll be upping the nutrient dosing for NO3, PO4 and trace. My PO4 usually never goes over 2-3ppm so I don't think the increase will hurt anything. I will see if the increase in traces change anything at all. The hair algae is VERY minimal but if it's there at all I see that as a sign of something going on hence the reason I did water testing.

I just thought the uptake would be generally the same. However, different plants use varying levels of nutrients so I suppose that's a bad summation.

@plantbrain, I didn't realize that the KH/CO2 relationship was only based on carbonates. It makes sense now that you pointed it. It just never dawned on me. The more I learn about aquariums especially in regards to acid base balance the more I realize it parallels medicine. In fact, nearly identical for the human body. Thanks.

plantbrain 04-26-2013 04:49 AM

Nail a good trimming if you see any GHA appear asap.

Water change, spot treat the infested plants/area with excel, then wait a few mon, turn filter back on etc. Tweak the CO2 a little bit higher and watch very closely when you do this.

Adding more PO4 does not cause issues, near as folks can tell.
Some do this to prevent GSA, I'm not so sure it does.

Uptake of nutrients/CO2 is not linear.

Many assume that is it and many like to think themselves as very knowledgeable about dosing ferts. I really do not fuss much with ferts, but light and CO2 instead. that said, I know the basics and how plants respond over time to ferts.

It's sort of an intermediate level for many planted hobbyists, some folks need to get it out of their system and they run from each fert to the next and never see the holistic picture. Most of the folks do this, myself included years ago, but eventually you realize it does not matter much.

Thi is something many aquarist have to go down and experience themselves, does not matter what I or anyone else tells them. But they can cause a mess for newbies in the interm. Most figure it out later fortunately and then have both experience and knowledge to help new folks.

It's good to learn from experience as long as it's not your own, but many of us are not wired that way or that accepting. (Which is a good trait also!)

the CO2/HCO3 thing with people is pretty cool if you think about it. Like aquatic systems and plants, the gas phases for CO2 and O2 MUST go into/out of the aqueous solution for plants and animals/people.

If you change the pH of the blood/plasma etc with something other than CO2/HCO3........this can cause issues, same deal with planted tanks and CO2.

Now if the KH is entirely all HCO3.......then you are set.

There's a cool way to get around this, use a gas membrane with a reference pure KH HCO3 solution in it. Then a pH probe. the gas will go across the membrane, but not the acids, non carbonate KH/HCO3 etc.

This can be done for measuring Human CO2/HCO3 is such situations etc. I would assume that woud be the best method to avoid issues in the blood and other non carbonate KH.

Still, healthy patient vs healthy plant/livestock, you can see what works and if you adjust and observe SLOWLY. I have 3-4 different CO2 ppm's in each tank I have.

No one tank is the same as the other. Why? Not sure, have some ideas, but every tank is unique where than D range is.

CO2 also have a similar pattern.

Here's a good article on light and CO2:

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