Flow/Powerheads in 55 gallon reef tank

[reeftankdan]

I'm trying to figure out how much flow i need in my 55 gallon reef tank. I'm using 2 55 gallon HOB filters, and recently purchased 2 1050 GPH adjustable AC powerheads. I installed them up high and pointed them at each other and set them to the low/medium setting. I also have one on a timer to turn on/off every 30 minutes. I don't have a ton of livestock in the tank yet, just a Zoa and a Green Star Polyp, 1 clown and 1 blue/yellow damsel (+snails, hermits, etc).

My corals are loving it and seem to be thriving even more since adding the powerheads, but my damsel jumped out of the tank after 1 night, and my clown is hiding behind the HOB filter. I've had the water tested at the shop and they said everything looks great. Do i have too much flow in this tank for fish to be happy? Please help, i don't want to lose my clown and I'm nervous to put more fish in...

 

[reeftankdan]

Here's the powerheads I bought, if that helps any...

 

[vlangel]

I have a 56 gallon column tank and I have 400 gph out of the return and about 1500 gph from the powerhead. I have the powerhead in the left corner pointed toward the surface. None of my many fish are disturbed by the flow but my tank does have a lot of rock which interrupts and slows down the current in the tank.

 

[reeftankdan]

I have about 40 lbs of rock. I was considering aiming them down a bit instead of across the tank top, but i was worried about blowing sand and red algae around the tank.

 

[vlangel]

I would worry about that too, especially since your tank is not as high. If you aim the powerhead toward the opposite corner and somewhat ripples the surface, the flow will cross the surface of the tank, hit the glass and deflect in multiple directions. That should slow it down enough not to trench the sandbed or blow algae around. It's a bit of a tinkering game to get it where it maximizes the benefits without creating issues.