Can a blood parrot fish be kept in a 20 gallon tank?

I started off in a 20 gallon tank with my 2 BP, 1 oscar, and a few others, it was very hard to keep up with the water changes as they got bigger. They also faught alot. Now they are much happier in a 50 gallon. the water says cleaner too! So to answer your question, 20 gallons is ok for as long as they are still small and not too many tank mates. But as they say 'the bigger the better'.