I'm not great at this stuff but I have previously posted lighting questions and have had great responses. 390 watts over a 55 gallon is roughly 7 watts per gallon and as far as I've read and heard you want 5+ watts per gallon to do clams generally. So I would say you're okay but another thing I learned is that halides might provide the same wattage as a p/c depending on your configurations that you compare. So lets say you have 390 watts from halide. Well I would say halide because I've heard they penetrate the water deeper than P/c's. Just something I've heard on forums. But I would ask around and see these guys are really knowledgable. I only run a
coralife Aqualight lunar light which has 4x65 p/c over my tank it's a 75 gallon tank but 18 inches to the bottom. I intend on doing a beginner clam eventually. As far as what I've heard on this forum I can do most things but not many SPS.
