Placement of Powerheads

[Blue Ram]

I've ordered another Tunze Turbelle 6125 for my 120 gal reef to increase circulation as I am getting some red cyano setting on the rock/coral and sand. Most of my rock and coral sits in the lower half of the tank.
I will now have 2 Tunze 6125 and 1 large hydor powerhead. The tank is 4' 120 gal with a large overflow on one end and two outlets at the other end. What would be the best placement for the powerheads to provide an even amount of flow throughout the tank and avoid areas of no flow?

[Gripenfelter]

Most corals have individual flow requirements. Some require high and some require low.

I have a 120 gal 4x2x2.

I have 3 power heads. All three are on the back of the tank. Two of the powerful 1600 GPH ones point towards the front middle glass of the tank with one head pointed more up towards the surface and the other one pointed a bit down towards the middle of the glass. My third is simply pointed across the entire back of the tank.

I'll draw you a diagram. The green arrows indicate how I had it setup before. The blue arrows indicate my current setup. New setup seems to make the corals happier. I have 200 lbs of rock in the centre. New setup leads to more turbulent flow which the coral seems to like.

[gobytron]

If it's Cyano you're looking to rid yourself of, try putting one powerhead right at the top of the tank blowing lengthwise creating airation at surface.

[Blue Ram]

If it's Cyano you're looking to rid yourself of, try putting one powerhead right at the top of the tank blowing lengthwise creating airation at surface.

This is the way I currently have it. 2 powerheads blow lengthwise and are placed very high in the tank.

[Lampshade]

try placing the powerheads widthways on the tank. With a coast to coast overflow you can disrupt a lot of flow having the powerheads pointing lengthways. For every bit of water the powerheads put out they need to take in the back side, so you are creating 2 opposing flows if everything is trying to flow in one direction. I noticed a lot better flow in my tank by moving the powerheads around a bit.

Lots of poeple like to create a barrell effect to pick up debris, I have my powerheads a bit more randomized, but for lots of people pointing powerheads widthways across the top of the tank will flow down the front glass and up the rockwork in the back of the tank(if that's how yours is placed).