Water changes and effect on plants fixing co2

Carissa

Guru Class Expert
Jun 8, 2007
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Hi,
I was just reading a post on non-co2 tanks and it mentioned in passing that doing water changes on non-co2 tanks adds co2 back into the tank. Would this be true if the water was allowed to age first? And what about if the tank had very good circulation to begin with? I'm thinking, it seems better to not be adding extra co2 if possible, since this causes the plants to stop producing Rubisco, right? Then the rest of the week they are at a handicap once the addition of co2 has equalized again. Would it perhaps be better to make sure water is aged and the tank is very well circulated if you are doing a non-co2 tank, especially with weekly 50% water changes?
 

Tom Barr

Founder
Staff member
Administrator
Jan 23, 2005
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The main issue is to keep the CO2 stable, does not matter if it's 1ppm, 3ppm, 10ppm, 30ppm.

Folks assume that their one measurement is the same throughout the tank and for every plant on equal terms, they also assuem that the CO2 ppm is the same throughout the day.

Both are poor assumptions, howeverm many still insist their CO2 is right and that their test are infalliable, and they still have algae etc.

CO2 is the key issue for plants and the most common limitation to Aquatic plant growth.

It's not too many or too few nutrients in natural systems............

But some hobbyists like to speculate that's why they have issues........

Regards,
Tom Barr
 

Carissa

Guru Class Expert
Jun 8, 2007
678
0
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So from what I understand, if I were to age tap water before using it for a water change, it should come to equilibrium with the atmosphere. Then, I just need to try to get my aquarium water to be more or less at equilibrium with the atmosphere too, which I can try to accomplish by getting as much circulation as possible throughout the tank. Thus, co2 is more stable from one water change to the next.

On the opposite end of the spectrum, if I were to have little circulation, assuming the lights are on, the plants are using up co2 faster than it can absorb back into the water and faster than fish can produce it; then I do a 50% water change and dump in a whole bunch of tap water direct from the tap, with lots of co2... co2 levels shoot up...unstable.

Are these assumptions correct or is there a variable I'm missing?