Suction zone from powerheads

[Miami Reef]

I’m having a weird flow issue in my tank. I have two powerheads on opposite ends pointing toward the center, but on the left side near the bottom, I’m getting what feels like a suction zone. Corals in that area get pulled constantly, even at low flow. I tried changing angles, reducing power, adding a piece of rock, and even turning one pump off, but the undertow or return flow still happens. It seems like a return loop is forming no matter what I do

pic with a drawing

Video of the suction





The right side of the tank does not have this issue. The middle of the tank with the brain corals are also not affected.

 

[Miami Reef]

The aquascape is a vertical-style rock pile positioned in the center of the tank not attached to any side walls. It’s mostly a tall column with minimal overhang or horizontal spread.

 

[Red_Beard]

I had the same issue for a while. I was able to solve it by adding a little more rock to cause turbulence and create a little more randomness. Dont know how feasible or desireable that would be in your case (tank looks great as is) but that is a potential solution. The other thing you could try is aiming your return nozzle into that suction zone to compensate a little. With an rfg, that might break it up a little.

 

[ReefQuestCorals]

I mixed up the style of my powerheads to overcome this issue. The middle of my tank was the same from the cross flow. So I put a wide flow wavemaker on the other side to combat the flow from making such a dramatic suction. Kind of crashes together now and creates more random flow

 

[VintageReefer]

I’m having a weird flow issue in my tank. I have two powerheads on opposite ends pointing toward the center, but on the left side near the bottom, I’m getting what feels like a suction zone. Corals in that area get pulled constantly, even at low flow. I tried changing angles, reducing power, adding a piece of rock, and even turning one pump off, but the undertow or return flow still happens. It seems like a return loop is forming no matter what I do

pic with a drawing

Video of the suction





The right side of the tank does not have this issue. The middle of the tank with the brain corals are also not affected.

I have that on one side also and utilize it. I put a favia colony in the corner there. Whenever the sweepers comes out they get pulled upwards towards the powerhead and not adjacent corls

 

[VintageReefer]

After I realized they are always pulled up and away, I was able to add more coral nearby with no risk