Great article!!  I did not read all 23 pages.  Just one question.  I have a 90 gallon aquarium with discus in it and want to minimize the amount of current in my tank.  I am pondering doing just sponges, with a particle filter on an aquaclear powerhead.  I have 9 discus in there ranging from 3" to 5" in diameter.  I also have 12 hets, and 6 rummy nose, and 4 cory cats.  The tank is planted and I do water changes every other day.  Was thinking of doing 2 50 gallon sponge filters.  A brand named deep blue.  New to the market I believe, but they are available at my lfs.  What are your thoughts please.  I am currently using an aquatop cf500uv to filter the tank, but I want to use if possible solely the sponge filters.