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· Banned
2,072 Posts
Try this:
Add 2ppm of PO4
Add 5ppm of NO3

try for 3 weeks

Next try
Add 15ppm of NO3
Add 0.5ppm of PO4

Does the ratio matter when you keep these general ranges?
Nope. Not one bit in terms of plant growth. Ratios don't mean much till they become limiting.

So if you keep things in non limiting ranges, the ratio does not matter.
Yuo might waste a little PO4/NO3 during a water change so that might be a reason to achieve a ratio but the ratio in and of it's self does little till something becomes limiting.

Another question: how much is too much PO4? What level will it cause algae to bloom in a planted tank? I don't know the answer, but I can tell you it's very high, above 2ppm for my own curiosity and others have gone way beyond that with no ill effects.

Plants will store enormous amounts of PO4. That was the issue in the past when measuring lakes for PO4 content, they measured just the water and the algae floating in the water, they did not measure the aqyuatic plant biomass as well. This gave false assumptions about PO4 and algae.

PO4 can be removed within hours after adding it and plant responses are around 30-40 minutes.

Blindly adding anything is not a good method by any means, there will always be a fraction of folks that do that no matter what you say though.

I was one of those folks:) Still am in a way. I just don't listen and have to try it myself.

While many seem to approach things from the minimum apporaches, I went the other way, what are the maximums?

I don't know what the max levels are for NO3 or PO4.
But they are quite high, same for traces and K+ and GH(Ca/Mg).

I've had tanks with NO3 at 75ppm
Two tanks are around 20-30ppm of NO3 at present(no fish, all inorganic KNO3)
PO4 to 2ppm
Ca levels to 600ppm
Mg to 60ppm
K+ to over 50ppm(Erik said he went to 100+ppm)
Traces to 10mls per 20 gal daily.
CO2 around 30ppm is saturation levels for aquatic plants no matter what light you have.

Minimums will vary somewhat species to species, some can handle low NO3, some cannot.

It's nice to approach things from a minimalisty prespective. It helps to see what effect each nutrient has, but if you approach this from a minimalist prespective what about CO2?

Should not we add only "enough" CO2 therefore also?
Have a non CO2 tank?
What does that "minimal" mean?

As little as possible and still grow plants?
That seems to be a recipe for stunting plants if you ask me whether it's CO2 or PO4 or NO3 or Fe.

I'd rather have non limiting ranges that are not so rigid and easy and flexible to maintain. Having most in the higher ranges, the maxes or reasonably high will prevent anything from bottoming out withotu wasting much during the water changes.

If getting the most out of your nutrients is the goal:try this approach:

Keep the other nutrients at non limiting levels and manipulate one nutrient at a time going from low to high.

When adding more of nutrient X no longer has any visual enhancement at a given light level, you have found the max amount for that tank and biomass/plant species type.

This max level will be different for different tanks.
But a close approximation can be achieved and generalized for most planted tank since the max levels can be higher without ill effects.

So a high light tank will have the highest amount of nutrients remove and the most added, any less light will be excess unused nutrients that are removed during a water change.

This does not cause algae.
NH4 from fish waste beyond the capacity for the plants and bacterial uptake will cause algae.

Hope this helps

Tom Barr

Tom Barr

· Banned
2,072 Posts
Do you have a reference for that UF study? I work here at UF and know everyone at the Aquatic weed center andn in the Botany Dept.
I'd be interested in seeing who did the study.

I think you mean MW's "carbonator" and not the "vital" stuff?
The Vital is a bottle of enzymes and does nothing for planted tanks near as I could tell over the course of several years that I tried it off and on.

As far Excel/Carbonator products, they cannot grow plants faster than CO2 alone. That is what plants and algae prefer over intermediates and what plants can use best as the CO2 is much smaller and easier to assimilate in the Carbon fixation/reduction pathway.

From what I've seen, the products do not go beyond about 2w/gal without help and CO2 is still better and more able to produce better plant growth under non limiting conditions.

If you cannot use CO2, it's better than nothing but it's not going to replace CO2 and cost a fair amount over time.

As far the usefulness etc of Marc's product the carbonator, it does the same pretty much as the Excel. So while many poo poo him for some things, the product in question here does work, not as claimed, but it is a decent product like Excel.

In order to find out if the Excel is better, you need to try several light intensities, different concentrations. For CO2 to be non limiting at most light intensities, the concentration needs to be about 30ppm for most species of plant.

If the study used something like a bicarb user like Hydrilla, measuring how much CO2 came from the HCO3 vs the Excel would be a very interesting question. Using a plant that has to use CO2 only like mosses would perhaps be better.

Gas exchange studies are not easy and tend to require substantial work to give significant results that are of use and really answer a question well.

Tom Barr
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