well if there is more than 2 in the tank then it is probably mating behavior. if u see 2 staying together and picking on and chasing the other or others away then i would remove the pair and give them there own tank. rember that angelfish are of the cichlid family and they can be mean during mating and breeding. there's a thread in here called wigglers at last and u will find tons of help there. me and a few others are breeders of angel fish there. feel free to pm me with any questions.