# Water Agitation and Oxygen versus Carbon Dioxide



## Samkim (Feb 3, 2012)

Just finishing up stocking my 65g tall tank with fish and plants. I've got a HOB filter as well an UGJ set-up to create a pretty good amount of surface agitation and water circulation. My initial thought with this was to create enough agitation to keep my water highly oxygenated so the fish would 1) have currents to play with and 2) be able to breathe!

How do you guys balance the increase in oxygenation resulting from surface agitation with the release of Carbon Dioxide? I'm concerned that I'm agitating the water enough to expel the Carbon Dioxide that my plants will need to grow properly. Should I consider putting my HOB onto a separate timer to leave time for the Carbon Dioxide in my tank to build so that when I turn my lights on and the plants start consuming it that they'll find sufficient supply?

I've got java moss, fern, and a few other low light/hardy plants (sorry, can't remember names!)

Just trying to get ahead of any plant loss I might experience. I've thought about CO2 injection but figure that the agitation will still release the CO2 I am introducing!

Should I, first, bring a sample of my water into the LFS and see what they find?

Thanks for your help,


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## Number6 (Mar 13, 2003)

agitating the water can increase or decrease CO2 levels... depends on what it was at. 
Gone are the days of planted tanks where the water was kept still to keep CO2 levels artificially high. IME, if you aren't injecting additional CO2, then you want to agitate the water a ton so that the water is areated and keeps the CO2 level up courtesy of atmospheric CO2.


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## BillD (May 17, 2005)

I have to agree 100% with Number6. This is something that is overlooked in discussions about planted tanks without CO2 injection. If the plants are consuming CO2, it stands to reason that more agitation will allow the tanks to more easily reach equilibrium with the CO2 levels in the atmosphere.


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## shocker123 (Mar 20, 2011)

Now will this help control algae in a non planted tank?


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## Samkim (Feb 3, 2012)

Thanks for the help guys, I'll leave my HOB return and UGJs alone for now (at the level that I enjoy) and monitor plant growth. If they start to turn south I'll bring my water in to a LFS to see what they might say about it and also bring up my concern about CO2

Hopefully none of that is necesssary, though


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## Number6 (Mar 13, 2003)

*Samkim*
no LFS can measure CO2 levels reliably as your sample tank water will not stay the same as it was when it was in the tank. To measure the CO2 levels, you measure your KH and pH. By checking your pH at a few key points int he day (morning, noon, night) you can reverse calculate the likely CO2 levels according to some charts floating around the net.

*shocker123*
healthy planted tanks are one where the plants grow and defeat algae without your involvement. Focus on the plants, not on algae...


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