Depends on the coral... I personally feed my tank DT's (for the pods and such), Cyclop-eeze or Golden Pearl and Formula 1. IMHO few photosynthetic corals "need" direct feedings but I like to feed them anyway (just be sure not to overfeed). Some corals can eat larger foods such as pieces of shrimp... I like feeding my candy cane & frogspawn & other LPS corals pieces of "thawed" frozen formula one.
Back to the Reef Solution, IMO these types of additives are a waste of money and can be a cause of increased nutrients in the water. Water changes does the trick for me... but with the magnesium I do test and add accordenly... if you are adding Iodine & strontium I'd recommend testing to see if the water is deficient first.
I'm all for soaking fish foods in vitamins, garlic and especially Selcon or Zoecon for tangs but I would not recommend just adding these to the water... IMO doing so just adds to the nutrient levels and have little benefit to the fish themselves.