I just wanted to share what I did in the past with a freshwater 55g I had a few years back. (Started a saltwater recently). I purchased a very long stone bubble bar and placed it UNDER the gravel at the back of the tank. All the bad stuff was sucked right into the gravel. However, I would do a full cleaning of the tank taking all my fish out every other month. Worked like a charm. No filters to buy and the tank always looked clean. The gravel bed was 1 1/2 to 3 inches deep completely covering the bubble bar. Just a thought if anyone was on a tight budget like I always am.