What are the co2 shots I know the plants need the co2 but is it liquid and about how much does it cost?
Good question, I'd like to know that too! Anyone?
Co2 is not a liquid unless under pressure, otherwise it is a gas. Products such as Excell are not CO2, but an organic carbon source that plants can use. I am not sure what product you are talking about, but if you have a link or a name I will be happy to take a look at it.
So how do you put it in the tank
It is put into the tank as a gas and is dissperesed as bubbles and the longer it stays in contact the water the more is absorbed but you have to be careful becasue too much can kill the fish and it can also cause PH swings. I think over 30 something is bad.
I don't know much about plants but as for pH it is true the water will become more acidic if u add too much CO2 just to warn you which way it will swing to the lower side of the pH scale. fyi