The flow through it doesn't really matter. It's just the actual flow inside. Since you want frags (I'm assuming some sps
) your going to want to have a decent flow, so a couple power heads will be sufficient. I would go for atleast 20x overturn. I have that in my 150 predator reef and I'm going to add more power heads to get it to about 35-40x so you may want it in that range.