This personal experience is sort of tangential, but I think it demonstrates that any given fish will go polygamous. I used to have several pairs of angels, which are noted for the strength of their pairing bond. One day I had to move an established ppair out of their spawning tank into a 55-gallon community. Three days later I came home from work and found the male spawning with a second female, while his "first wife" kept all the other fish in the tank pinned against the far wall. Thereafter for the next year, the trio lived peacefully, and the male would spawn whenever either of the two females was in the mood. Sometimes he covered both females' spawns simultaneously, with excellent fertililty rates. He died at a young age, can't imagine why. Bob Dixon