Arrange the power heads you already have until you get them to move water in all areas of your tank. Get a stick and attach a thin piece of ribbon to it and move it around in the tank to see were your flow is or isn't.
I bet you have phosphates so that's a test you need. I run Purigen, it costs extra at first but you can reactivate it and use it over and over..
Also feed your fish only once each day...saltwater fish have more to eat than you realize, because they nibble at the rocks, feeding on the little critters in there. So they will not go hungry believe me.
So many folks don't like them, but hermit crabs LOVE brown algae and will eat every bit of it up. I like them and I happen to like them better than snails for a CUC, when it comes to a good job they can't be beat. I like serpent stars over brittle stars as well.
Green algae (not hair algae) the fish eat, what kind of algae eaters do you have?