my 300 has a 5 inch asfur and 5 inch regal angel in it. i have a crocea, deresa, and maxima clam in there that they never touch. i recently bought one of those large maximas which shipped poorly and died on the second day in the tank. the angels ate it before i could get it out of the tank. but they still leave the other clams alone. i view clams with angels as a measured risk, tomorrow they may eat all 3, but so far so good. angels are not predictable but i think it is worth trying as i like both angels and clams.