55 is too small IMO. 75 and up would be preferred, but the 55 may work for a while if they're young tank raised fish. Make sure you have excessive filtration and powerheads that can move alot of water. For foods, I use NLS, dainichi veggie deluxe and fx, and hikari excel as base foods. I also feed chopped krill and mysis 3x a week. Make sure you have metronidazole and clout on hand before you get the fish in case any illness pops up. Weekly water changes are a must. This is an extremely limited overview, but covers most of the basics. Consistency is key with trophs. Foods, lighting schedule, water changes and chemistry should be consistent and radical changes avoided. The first month when getting new trophs is extremely critical in making sure they stay healthy. Once established they are extremely hardy fish.
Have fun!