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I have never tried the experiment of keeping a clam exclusivley under blue light. Most clams come from fairly shallow high light water where they receive natural daylight. Daniel Knop suggest that they should be kept under 6,500k lights which is the sort of spectrum in the shallows. However, myself and others have not had a problem with 10,000k lights. I have no experience of higher kelvin lights and do no see any benifit to trying them as the clam colours seem to show off great under these lighting schemes.
?? I am confused about your part of the post which say 6100K actinics ??
Clams do need alot of light and in general I would recommend 250W MH lights and also remember to feed them phytoplankton.