Did you take the sponge out to keep the nitrates down? I took mine out for that reason and then noticed lots of gunk accumulating on the plastic drain (the one that is normally covered by the sponge). I was afraid that the gunk would begin to obstruct the drain so I cleaned it off and put the sponge back on. Now you've got me thinking that I should take the sponge back off... what do you think? How long does it take for nitrate producing bacteria to start colonizing on the sponge? Should I leave the sponge on and just rinse it in fresh RO
water every few days or just leave the sponge off completely?