NO3 and PO4 vs N and P confused many - The Planted Tank Forum
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post #1 of 2 (permalink) Old 01-22-2013, 10:04 PM Thread Starter
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NO3 and PO4 vs N and P confused many

i think many people are confused with understanding the difference between these elements. they think they are dosing way too much Nitrate and phosphate when dosing EI vs other fertilizers such as seachem, TPN etc. i use to be confused as well when i look at seachem Nitrogen which shows that it adds 1.5 N, when dosing EI we follow NO3, 1.5 N is more than 6ppm of NO3. we can reduce those 6ppm to 4ppm since Seachem uses Urea, lets say seachem nitrogen adds 1ppm of N. same goes for phosphate, 0.6 P is 2.0 PO4, again this might confuse people even more because most people are use to NPK and they take No3 and Po4 as a N and P, which make them think they are dosing way too much and they will reduce there dosing to those NPK numbers while using No3 and Po4 numbers. i have done this in the past and blamed fertilizer for failure to grow plants, am sure most of us out there are still confuse with these numbers and we all make mistakes and we all are not very good with chemistry, i will admit am not.

there are few things which still make me confuse, when we test for nitrate when dosing EI, we get higher reading on the API test kits, if plants are really using the nitrate then why are we still getting high readings of nitrates?? if our test kits detect 20ppm (NO3) of nitrate that mean we have around 4.5ppm (N) of Nitrogen, organic or inorganic. some people are afraid to dose more Nitrate because they are already reading high nitrates on their test kits and they also expereiece plants stop to grow, why arent the plants growing?? this make them more confuse.

most of people are not aware of NPK and NO3, PO4 numbers, they are confuse and make many mistakes, most of them come here asking why arent there plants growing when using EI, they must be looking at wrong numbers, IMO.

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post #2 of 2 (permalink) Old 01-22-2013, 10:29 PM
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The biggest longest running mistake is mass vs atomic ratios.

Redfield ratio is 16:1 for N:P, this is atomic.
It's off by a factor of 2.2 or so if you convert to mass.

Add the NO3: PO4 and you add even more issues.

Generally, I've not found any examples of long term uptake that exceeds more than 3-4 ppm per 24 hours of NO3.

For NH4, this is about 0.8 ppm per 24 hours.

Virtually every single aquarium will use LESS than this.
This goal is not to dose exactly some specific ppm, the goal is simple: provide nutrients, so that nothing is even in short supply.

This range is roughly 10-30ppm, I tend to keep my tanks in the 10-20ppm range for NO3. PO4, this is less important, but seems to get a free pass these days(that was hardly the case 10-20 years ago), but anything from say 0.4ppm to 5 ppm seems widely used.

Uptake here can vary widely depending on dosing frequency. I dose 4-5ppm 2x a week. I use to dose 1 ppm once a week, some dosed 0.2 ppm 2-3x a week, others dose daily 0.1ppm etc.

I have folks asking me why their ADA tanks are filled with algae, or why the Seachem stuff causes algae or their plants are not growing either. 9 times out 10, it has little to do with the N vs NO3. Sure, we correct them and get them back down, but it will not save them from the original issues that they have, too much light, not enough current/CO2 etc. Those 2 issues have not changed since I've been on the internet, so 18 years now.

If they have 60-100 ppm of NO3, well, then they likely have other issues and are not doing the water changes etc. The target is 10-30ppm, most folks should EASILY be able to hit that. PO4? I do not know, maybe 2-5ppm. I do not see much difference.

CO2? light? Massive differences.

We have dosing calculators with both raw chemicals and brand name products, so the folks can use those if they are aware of them. Plug and chug.

Tom Barr
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