from what i have been told you need metal halides or a good amount of t5's (like 8)to keep clams healthy said:
That was poor information that you were given.... its the amount of light that is important, not the type of lighting. People have kept clams very successfully with PC and VHO lighting for many many years.
The only times I have seen a clam bleach was from lack of light, or ammonia.... lack of light they will color back up fairly soon. Ammonia killed the other one.