Planted Tank Enthusiast
Join Date: Mar 2007
Location: San Antonio, TX
if you're using DIY co2... none of those difuser's will work as DIY co2 usually can't produce enough pressure, safely, to push co2 through the disc.
and just for kicks, the third on you posted doesn't attach to the aquarium wall or anything and the fourth one isn't a difuser, just a bubble counter.