To be honest, everyone I've known who've had packed SPS tanks, including @glennf
have just let them get on with it. Obviously within reason, but when it's getting dense, you just have to let nature take it's course.
If you're much less densely packed than that, just space them out based on aggression. I don't know much about SPS aggression, but it's well documented with LPS. So there should be some guides or info about SPS aggression.