I have never had clams before, and dont know anybody personally that has. I have a freshwater tank. Is it true that they improve water quality? What do they eat? How do i feed them? How often? How do they grow? How many can/should i get (see signature for current stocking and tank sizes)? Is it possible for my betta to break shells? How many can fit in his tank if not? Are there different breeds that are commonly sold? Do Pennsylvania Petsmart or Petco's sell them and whats typical price. If not, will ones i pick from river be fine to use? Answer as many of these questions as you can please. Thank you for your help.