Need a little help*understanding plants photosynthesis

I think it would be better to start air pump immediately after light-off.

CO2 can linger long in the tank. With my new and taller than before tank,
drop checker would still be green even hours after turning off CO2 if surface
agitation was not enough. And even though I had increased agitation, the tank
seemed to lack O2 somewhat that the critters were OK but organic matters
didn't degrade well (leading to BGA even with OK level of NO3).

At first I couldn't find where to place an airstone without creating splash.
Then I got the idea of putting it into the surface extractor.
And that improves things.

 

Increase water circulation in the tank, you can use a power head.

 

We All Like To Breathe 24/7/365

Hi,

Remember that plant respiration goes on 24 hours a day. :gw

You said you have a “heavily planted tank,” remember that as photosynthesis ends the plants go from net producers of oxygen to net consumers’ oxygen.

A little surface agitation and increased circulation, whether by air pump, powerhead, redirecting water flow toward the surface will go a long way toward keeping flora and fauna happy.

Biollante