I have purchased the tetra co2 optimat for my 10 gallon planted tank. I followed the instruction for the complete installation but still it seems like it is not working properly. I add co2 from the depot but the green canister keeps filling up with water. Water comes in pushes its way up to the middle of the canister while bubbles are being released from the side. So i cant fill the whole canister with co2 like im supposed to. Is that normal at all ? I would appreciate any help.