I need help getting a pair of Bangai cardinal. How do I find out if it's a male or female. I don't want to spend the extra money on getting a pair already. How many should I get to try to get one or maybe 2 pairs. I only have enough room for 4 2 in my 55 gallon and 2 in my 20 gallon. My idea is to but around 4 in the 20 then once a pair forms I put the other 2 in the 55.