Preventing constant central flow to overflow

mfollen · Jul 7, 2023

Hey all,

In my 5’ wide x 4’ long reef, I have had trouble preventing and minimizing a strong constant flow from the far end of the 5’ tank that builds through the center of the tank towards the overflow box.

This has a negative effect on SPS, and prevents where I can place coral. This is impacted also by my powerhead placements, as the tank is essentially a very wide peninsula tank. I have done my best to avoid placing powerheads on the visible end of the system, with pumps on the back and back sides of the tank. A visual of the tank and the water flow (arrows) can be seen below:

I have experimented with varying and random powerhead flow schedules, but the problem persists.

I have reached the point realizing that I will need to relocate my powerheads. The system is primarily built of 2 MP60s and I have 3 MP40s to work with and two gyre pumps.

I would like to achieve the swaying back and forth swooshing flow, but also the alternating gyre around the edges of the system, achieved with the two MP60s on the back ends of the tank (pictured above).

I am thinking that maybe I will need to put two MP40s at the top of the 5’ sides set for the pulse mode.

I wonder what else I can do with other configurations, even with the gyres to get rid of this constant strong flow through the center of the system to the overflow. I can lower my return pumps which I have at a high level, to maximize detritis input into the sump.

I am open to all ideas as I’d like to experiment with the powerheads this weekend. To note I currently have a gyre mounted in front of the overflow box (as pictured in the above picture) to fight against this flow, but it can only fight back slightly as flow goes up and down.

Thank you everyone for any ideas!!

blaxsun · Jul 7, 2023

Where are your return outlets?

mfollen · Jul 7, 2023

Ah yes I should have included that.

They are on the upper back corners of the back wall. I do have long fingers to a RFG pointing to the center of the tank against this central flow

mfollen · Jul 7, 2023

Picture updated here w/ returns

o2manyfish · Jul 7, 2023

Assuming you have rockwork in the center of the tank, Getting a pulse flow may be difficult cause you are shooting into the wall and the reflection off the wall is coming back an neutralizing the wave.

You could try placing all the pulsing pumps together on back wall to the outer edge of the aquarium. Then experiment with the delay in pulse till you get the right frequency for your tank.

It can take a long time for the pulsing wave to build. It doesn't always occur immediately. I have one tank 8x3 that the wave builds up to 2-3" and then subsides down to .5" and then builds back up again.

In my 10x4 tank to get the swaying motion required putting a pump facing the long ways down the tank. But I used a really big pump - An Abyzz Flow Canon AFC-150.

I'm not familiar with the pulse settings on the MP40s. But I know with the newer Panta Rhei ECM 42 you can set the pulse speed hi and low and the time between the pulse in very small increments. The Panta Rhei is a pretty amazing pump and there is a good chance just one of those pumps set correctly for your tank would pulse the water back and forth.

It may take hours, frustrating hours, to find the right timing that works for your tank

Dave B

mfollen · Jul 7, 2023

Fantastic thank you Dave, this is great insight.

Indeed I have already spent many hours tinkering and monitoring subtle changes in flow and placement of corals, just to ensure a frag doesn’t get ripped. I’m willing to hit the reset on the fine tuning I’ve done so far to get this right.

How long did it take for the pulsing motions to take place in your tank?

And for your panta rhei pump, how much time in between the high and low pulse settings do you have it set up?

Thanks again, and I’m open to all opinions and experiences here as I try to map out the best way to utilize these pumps.