[niko]

If you put the sponge where I suggest you will see exactly what I described.

Using a sponge to avoid sucking snails or baby shrimp is fine except that it needs to be cleaned on a regular basis. If you are consistent with cleaning the sponge then the CO2 reactor will have no problem. But if you let the sponge get dirty the water flow will decrease and the amount of CO2 being disolved will also decrease. This may not sound like a big deal but it actualy is because fluctuating conditions in a planted tank are the main cause of problems.

--Nikolay