Aquatic Plant Central - View Single Post - CO2 fluctuations in a non-CO2 tank

R0bert · 02-20-2006, 03:05 PM

The graphs are a little misleading because the ph at bottom right is different for each one. This makes the ph swing seem much bigger than it actually is.

I wonder what the KH is?
If we assume that the ph controller being set at 6.2 is trying to achieve around 30ppm CO2, then we assume the KH to be 1.5. Therefore the PH swing at night is only from 1.5ppm to 3.5ppm.

I have read that around 3ppm is what you would get from the atmosphere without any CO2 injection.
So during the day the plants use up 2ppm CO2 in photosynthesis and at night the atmospheric CO2 slowly goes back into the tank.

BTW When I let my KH 12 water sit, ph is 8.5. Does that mean high KH water will absorb less CO2 directly from the atmosphere?

02-20-2006, 03:05 PM	#6 (permalink)
R0bert Junior Member Join Date: Jan 2006 Posts: 20 iTrader Ratings: 0 Plant Points: 3600	The graphs are a little misleading because the ph at bottom right is different for each one. This makes the ph swing seem much bigger than it actually is. I wonder what the KH is? If we assume that the ph controller being set at 6.2 is trying to achieve around 30ppm CO2, then we assume the KH to be 1.5. Therefore the PH swing at night is only from 1.5ppm to 3.5ppm. I have read that around 3ppm is what you would get from the atmosphere without any CO2 injection. So during the day the plants use up 2ppm CO2 in photosynthesis and at night the atmospheric CO2 slowly goes back into the tank. BTW When I let my KH 12 water sit, ph is 8.5. Does that mean high KH water will absorb less CO2 directly from the atmosphere?