Population control? As in keeping the fry in check or the live bearers? Wouldn't that make the Firemouth more aggressive? I am intrigued. Which is partially why I am raising a shrimp tank to potentially use as live food. Although, I haven't really got into doing that just yet. It would be really cool to watch! I feel like it would be having the Discovery channel right in my own house! It can get expensive if I exclusively feed them shrimp. Of course I wouldn't do that anyhow. I like putting variety in their diet.