I use these in one of the media drawers of my Fluval 307 and it added an extra layer of filtration that has kept my tank cleaner longer. Instead of having to do a water change every 4 days, i can now make it a full week before cleaning out. I usually get 3 good water changes out of these. I could go a month but my fish have gotten bigger and poop a bit more than when they were smaller.
Rating:
[5 of 5 Stars!]