Mines tail is red also, its in my album as african cichlid. I feed him crumbled up cichlid sticks. It took him a while to figure out what food was, but now he begs and dances for it.
It looks like what you have is a nile tilapia, probably an escapee from a local farm, or more likely offspring of escapees. Anyways, any primarily vegetable based pellet or flake should work.
Looks like the pond I got it from stocks tilapia to reduce algae buildup. Although they don't look anything like my fish... Here's one I just caught this morning.