I have found that the key to clams is in their size. If you get the really small ones, like under 3-4 inches, they are still using phytoplankton to feed off of, which is something our tanks usually lack. When they get larger, they rely solely on light and water chemistry and IMO become very easy to keep, and are tolerable and *may* even prefer slightly "dirtier" water with higher nitrate than the typical sps tank.