thanks guys! the bgk is pretty fine!! my algae eater is yellow (gold), and my leopard pleco is about to be given to a friend.. because there is no enough space here for him!! i have put the new angelfish in a net, because i thought that the old one will get used to it before it kills it!! thanks..
!! if i add another angelfish the old one will attack both?
This is unpredictable. Like humans, each fish is a bit different in temperament. All we know is what is likely. A male angelfish, like most cichlids, regards the aquarium as "his" space. If a group of say 5 angels are introduced together, they usually
establish a pecking order, with the dominant male and the subordinates. Sometimes the "dominant" will tolerate the others, occassionally he will not, as a couple of other members here have noticed.
When a single angelfish is placed in an aquarium, and it is a male, he usually establishes the aquarium as his territory. If other angelfish are subsequently introduced, he may or may not tolerate them. Females are usually tolerated, but again not always. Males also may or may not be, usually not, because the dominant sees the other as intruders into his own space.
Sometimes the aggression is just bullying, like pushing and shoving; sometimes it is very physical. The subordinate fish may be killed outright, or it may be frightened and highly stressed. The latter usually leads to death sooner or later.
In the wild the fish are able to simply leave the area of the dominant fish. That opportunity is not available in any aquarium unless it is huge, as the closed system means the fish are all sending out chemical signals and recognize each other.