I would def recommend powerheads, its not only for the coral but for your live rock too. The more water circulation you have the less likely you will have dead spots where things accumulate like uneaten food and other things.
You get flow from the sump return and/or filters as well but nothing like you'd get from a powerhead
180g Reef - 60g Rimless Reef -90G FOWLR- 125g Malawi Cichlids- 40b REEF- 34g Fresh Planted-working on- 20L FOWLR- working on
I have a mix of many different saltwater fish amongst my tanks, but I love my Tangs most of all.