I have a 90g display with rather high Nitrates; trying to finally get this under control by using a sulfur denitrator, I have the small Aqua-maxx. The problem I'm having is with the 1 drop/second for a while, I get gas forming inside (not the sulfur smelling kind), that I then worry will be too much and damage the recirculation pump. I can let it out through the vent valve, but at the slow flow it just creates more. I had one day where it seems it was dialed correctly where at 1dr/sec I had like 0.1 nitrates in the effluent, so I turned up the flow to 2dr/sec, but then the air inside accumulated again and got in the way (I turned up the flow to get rid of it, and I suppose reset the unit again). Thanks for any advice, comments, etc. --Lars