I recently purchased a 100gal tank used from neighbor. It came with two 6mos old Eheim Professional canisters 1 wet/dry 1 regular. I am probably going with a sump/fuge, so what can I do with these canisters. Not enough water volume to just add on for more mass. I would like to use these instead of a sump if it would work. I've heard so much about excess NO2
, in the media though. I plan on a no fish reef.