Praecox-Rainbowfish(Melanotaenia-praecox), These are a lovely shoaling fish and fairly peaceful. I have kept these before and they are easy to sex as males sport a red outline to their fins whereas the females are more orange/yellow. Not suitable for small aquariums as they are a shoaling species. These fish are getting very popular with aquascapists as they don't eat the plants. They do however need good water flow and clear areas where they can shoal with some dense planting.