If you run a fish only system, then chances are you run canister filters or trickle filters with bioballs, and probably even have fake rockwork with fake coral inserts. While this setup may be easy to work with for the most part, it’s terrible in terms of filtration capacity and effectiveness. Fake live rock and corals simply don’t provide the surface area needed for bacteria populations to grow and thrive, leading to large ammonia spikes from feeding and fish poop that can’t be quickly processed into less harmful substances. On top of that, canister filters and bioballs can become clogged with detritus, further contributing to the problem. While we love fish only systems as much as any other tank, we highly recommend running them less like fish only systems and more like reefs, minus the corals and high intensity lighting of course. By that we mean that the tanks should be run with effective filtration systems (protein skimmers, large refugia, biopellets, etc) as well as with a stringent maintenance schedule. Perform water changes and clean equipment as needed, and be sure not to overfeed or let detritus build up in low spots in the aquarium.