What to feed a Molly fish in a saltwater tank?

My roommate and I decided to take on the daunting task of a 10 gallon saltwater tank. We added 10lb of washed aragonite, 4lb of dry rock, and 7lb of live rock. The tank has gone through a mini cycle from liverock dieoff. So I decided to get a saltwater molly to further strengthen our cycle (I figure the slower the bacteria is built up the more stable it will be as long as similar bioload is maintained).

Anyways, should I be feeding him tropical flake or marine flake?