I was considering getting some fresh water clams to add some natural filtration to the water. I have a 55 gallon, 2 10 gallons and 2 20 gallons. The 55 currently has a pretty good water turn over rate provided by 4 lee's bubble filters with a very high power pump attached. My angles thought they had moved from a pond to a stream when I hooked up the new pump! Any suggestions on breeds, placement or do's and dont's?