150w MH is the minimum for MH and can keep anything far better than FL/PL due to stronger light intensity that enables a deeper 'punch'.
Clams, hard corals eg. LPS, amenomes will do well with 150w. Some SPS and certain clams may require to be placed up higher to keep its colours.
For better growth & colouration of SPS and clams, higher wattage MH is recommended.
Do a search on lighting and you'll find a great deal of info here in SRC.