Some fish, angelfish included, will constantly seem like they are hungry, no matter how much you feed them. Don't give into them!
Overfeeding fish is worse for them than underfeeding them, and can lead to a shorter life for your fish.
Feed them sparingly, but a good variety of foods, if you can. Treats like frozen bloodworms or brine shrimp will make them happy, live foods are even better, but all in moderation.