Tomato Clowns are hardy and adaptable. They do get quite big- 4-5" and such specimens should probably be in at least a 75-90 gallon aquarium if you plan on keeping other fish. They can be aggressive, like all clowns and damsels, and should be housed with fish that can handle such aggression. They will soon learn to accept almost all food that you feed them. Quality Marine Flake or Pellet is a good staple and should be supplemented with carnivore treats such as live/frozen brine shrimp, mysis shrimp, plankton, krill, and fresh seafood. Tomato Clowns are known to host in Bubble-Tip Anemones and Carpet Anemones; I have also seen individuals host in Condylactis Anemones.
Unless you plan on getting at least a 50 gallon aquarium I suggest you stick to Percula Clowns.