Question for Tom about his non CO2 method

Harry Muscle

Junior Poster
Mar 17, 2007
I read Tom's article on non CO2 methods for planted tanks ( and I was thinking of following the advice almost to the letter since it sounds like such an easy setup. However, I do have a quick question or two I was hoping Tom or anyone else could answer for me.

First, is there anything that should be changed in that article (it's 2 years old so I'm wondering if anything new has come along that might have changed things)?

Second, how much Diamond Black (leonardite) would you recommend using in a 55G tank (I was thinking 3 pounds which would give me a layer about 1/4" thick ... about a 1 to 20 ratio with the flourite I will be using ... flourite is already bought).

Third, does the method have a certain life expectancy where after a couple of years the plants will start doing bad and there's nothing that can be done but to tear down the tank and restart things from scratch?


Tom Barr

Staff member
Jan 23, 2005
You'll note some weekly dosing suggestions in the article.
That adds ferts.
Fish waste adds ferts as well.

These, not just the substrate are the sources.
Leoardite just starts the process in the sediment of reduction until the plants take over and start controlling things.
3 bags of of it ought to be fine.

The substrate should be fine for decades, no worry there.
No need to tear down these tanks ever.

Unlike soil based non CO2 methods, the water column is continually resupplies in small amounts to prevent deficiencies.

So over time, the plants are not severely limited ever. They might be a tad tweaked, but nothing compared to fish waste and soil only. The substrate still becomes fairly rich with fish waste and plant detritus over time and gets better.

Soil loses it's fertilizer after a year or two, but then the plants are grown in and some fertilizer/fish waste is being produced to support some plants species that are aggressive and hardy enough to out compete the other plant species.

It's not just about plants competing with algae, it's about plants competing for
nutrients with eachother.

It's cheap and easy to add specific things to the water column to account for plant growth and to test. Sediment is much harder for a hobbyists to do these same things.

The trade off is very good as adding some ferts once every week or two is not that is not hard at all. It's cheap, anyone can do it.

Under dosing slightly and also allowing every so often a "period of nutrient decline" by not dosing for 2-3 weeks will help keep any levels very low.

Since growth rates are very are the effects of deficiencies/nutrient stress on plants. So those low levels are much easier to achieve using this method than say high CO2/light etc and still have decent looking growth.

This "rate of growth" can be used to our advantage.
We know that fish food does an okay job for supplying nutrients, but it's not universal nor balanced for the plant's demands, it's geared to health of the fish.

Topping off the plant's nutrients with small amounts of inorganic ferts and the limiting nutrients from fish waste helps maintain better growth than fish food alone.

Some suggest that the NO3/PO4 will rise, typically they do not and fish food is not the perfect balanced plant food. Even if the NO3/PO4 does rise, is that bad at a moderate amount? Does not appear to be the case in any research.

A purge by allowing the plants another week or two to remove it can help.

Additionally, due to the inherent flexibility with dosing dry ferts like this, you may add K2SO4, CaSO4, MgSO4, FeSO4, MnSO4 (GH booster) once a week and a spike of trace elements to force the plants to consume the limiting factors, the NO3 and PO4.

You may add these for a week without KNO3.
That will drive the NO3/PO4 down.

If NO3 is your concern, then adding the GH booster, traces and KH2PO4 will drive the NO3 down if you add everything but KNO3 for a week or two.

You can use the nutrients to force one nutrient of interest down every so often to "clean house". It's easy to do for any nutrient.

Takes a little while for the plants to remove it, but that's the nice part.

Tom Barr


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When I read the above it came to my mind if it was possible to convert a running EI/high light/CO2 system into a non CO2 system to prepare the tank for a certain period of abscence.

With my non CO2 tank I had little to no problems leaving it alone for three weeks with only one time feeding the fish in that period. No algae etc.

It would not be possible to leave a EI/high light/CO2 system alone for that period I suppose. It would not have water changes nor enough supply of nutrients ferts etc..

I was thinking if one could reduce the process slowly over a period of say 4-6 weeks until departure and restart again when back home.

Any thoughts?


Tom Barr

Staff member
Jan 23, 2005
As long as you reduced the lighting, things would be fine I'd say.

You'd still need to add water for evaporation, feed fish etc
The new growth would all be much smaller.

Tom Barr