Non Co2/excel Tanks And Water Changes


New Member
Apr 22, 2020
Hi all

I´ve been reading all your post related with dosing and water changes for non CO2 and Excel tanks. However, it is no quiet clear for me why I should do water changes weekly on Excel tanks and why it is not recommended for non co2 tanks if I use for both the EI dosing.

I understand that if I do a water change in a non Co2 tank, the co2 increases and the plant loses its enzymes. But in the post is recommended for both (excel and non co2) aprox the same dosing: “about 1/8" and 1/32" teaspoon of KNO3 and KH2PO4 respectively once a week or two”. Then:

  1. If I use the same EI dosing (above), why should I do water changes in excel tanks and not in non Co2 tank? Will not Both tanks have the same probability of have an accumulation of nutrients? In fact, I would guess that plants in a non co2 tank will grow slower and then, less nutrients are consumed.
  2. If I dose excel in a daily basis, (2x the recommended dose) what would happened if I do not add excel some days a week? is It mandatory to be steady with this excel dosing.



New Member
May 24, 2022
South Dakota
Excel is just hydrogen peroxide, which is slightly poisonous to everything but the plants. That is why people do water changes when they dose with it.

Rarely I do any water changes to any of my planted tanks. Just top off.

Because the main goal to my low tech planted tanks is to create the ecosystem that will take care of everything so the water doesn't have to be changed.

Like my aunt's end table lamps in her living room that have been growing swords in the lamp base for the past 40 years that she does nothing but add distilled water and cut the dead leaves out from time to time.


Super Moderator
Staff member
Lifetime Member
Jun 20, 2016
Excel has glutaraldehyde or the particular form polycycloglutaracetal as seachem marketing says, not hydrogen peroxide. You cannot see the same oxygen bubbles from adding Excel as you will see from using a H2O2 solution.

One can do the exact same weekly water changes on both tanks, the original article was suggesting that since non CO2 injected tanks will have a lower plant metabolism you can do water changes less frequently and accordingly reduce the weekly fertilizer dose.
The issue then becomes if Excel really adds that much carbon to the tank to increase plant metabolism to be on par with CO2 injected tanks. The answer is no. You can see the improvement 'liquid carbon' dose adds to plant growth here : and in some yt videos and so on. Interestingly, all these were carried out by aquarists... seachem has yet to publish such experimental data. Anybody still wonders why?


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Lifetime Charter Member
Lifetime Member
Jun 9, 2006
The only practical use for Excel IME is to spot treat BBA. Never had success using it as a "carbon" source and find it is quite hard on water plants at manufacture recommended doses.