Dosing CO2

[fishman1218]

Is it helpful, recommended or useful in anyway to dose a macro only tank with CO2 ?

 

[Amphiprion]

It can be helpful in many cases, but I don't know if it would be recommended in all situations, depending on the other inhabitants. Unlike freshwater, I don't know how you'd accurately measure it, either, seeing as how there are other factors that contribute to alkalinity in seawater--enough to be significant, IMO. If I were to use it in seawater, I'd start off as minimal as possible and work upward. While CO2 would likely have an effect on growth, I'd recommend just making sure your alkalinity is in check, which should provide enough carbon.

 

[A. cervicornis]

The CO2 will contribute to lower pH in the aquarium too, which could really accelerate dissolution of calcium carbonate substances in the tank like live rock or sand. Most people don't do it; like Amphiprion said, you can rely on carbonate alkalinity as a carbon source.