I am probably going to re-setup my 20 gallon tank. I've always wanted an electric yellow lab. Can it be by itself with no other fish?:huh: If not then can a firemouth?
The labs really do like to be with at least 1 or 2 other labs. With that being said I really would not recommend it even though the lab probably could survive. They will also most likely out grow that 20 gallon really fast because they grow quickly. I am not experienced with the fire mouth but I can assure you at a max size of 6" it will outgrow that tank.
Since you have specific species in mind, a quick bit of googling on those species show that minimum tank sized recommended for the labs is 50, and the convicts is 30.