I already have a male and female Apisto Cacatuiodes in a 20G tank and a few guppies in there. It seems a bit empty sometimes. I am thinking of getting an Agassizi breeding pair. Are there going to be any complications?
A very high chance that the caucatoides would kill the agazzis. Your tank is to small for more than one species. You might be able to add another couple of female caucatoides, but there is even risk in that.