i would say my lil guy is in the 3-4 month range. so the best thing i can do is wait till he/she can be for sure sexed. and if Gman is a she then i can pick up an sexed female around the same age. but if he's a male he's gonna be a loner the rest of his life. in that cause i got a 10 gal i can move him in to until he's big enough for the 20l i orginaly had planned for him.