well sometime you get lucky. The last time i put the smaller one in and they just live together, not a single bite. Anyway, get some eggcrate (spelling?) and divide the tank. if the smaller fish are being chase, it can just get to the other side of the crate and stay there. the big female can't chase after it. Oh yeah the most important question: is your smaller maroon a male or not? IF it is too big and not a male, then there is not point in putting two of them together. I can't tell a male from female either. I just drive to differnet pet store and get the smallest maroon i can find. I used to have such a hard time finding a small maroon to ensure it is a 100% male.
How big is your big maroon and how big is your smaller one?
Anyway good luck.