My output from my Fluval 404 says to put is above the water line..Why?? What would happen if I just pushed it down below the waterline so I didn't have to hear the waterfall sound? Is there a reason that it is supposed to be above the waterline?? I know that during set up that sound was responsible for numerous RestRoom breaks
They tell you that so that you create surface agitation. Helps with gas exchange by keeping the O2
level up and the Co2
level down. If you put it below the water's surface, not only will you not get efficient gas exchange, but you will also notice that with no surface agitation, you will develop a "skin" over the top of the water unless you have a skimmer or overflow helping to break it up. That "skin" is basically organic compounds that have collected on the top of the water.