40G Breeder Clownfish "Breeding" Setup Return Flow

[president89]

I divided a 40G tank up into 5 8G compartments, drilled 5 bulk heads and plumbed 5 return lines. The return goes into a loop back to the sump. The return line goes up into a T, one outlet goes back into the sump with a ball valve, the other goes straight up to my bank of 8G compartments. When testing a single compartment and the sump, I could not get a decent flow out of the one compartment, most of the water went back into the sump via the loop. Even when adjusting the return line's "Return" I wasn't getting a good flow. Do I need to add another valve after the bank of tanks to regulate the loop? I'm dealing with 3/4" PVC. Some pictures of my setup are below. Anyone have any feedback on my flow issues.

 

[president89]

I just did some extensive reading, and it appears that drilling a small hole in the return line just below the water line with the hole facing down (so water doesn't spew in weird directions) is a suggestion. Another was to create an air gap. The air gap sounds a bit more complicated. I wasn't able to find much on that. I have heard this is the same concept as the air gap created in dishwashers.

 

[flush102]

Was the valve on the return line from the pump wide open? throttled? or closed? Water will always take the path of least resistance. It looks like the valves on the compartment supplies are globe or gate valves?

I would start with the return valve closed and open each compartment up to desired flow rate.

 

[president89]

Valve on return pump to tanks open, return to sump was halfway - otherwise pump has too much power and water shoots out of return lines. Since PVC is cheap, and I'm not gluing in the return lines(the part below the top of the tank) I decided to drill two holes per return line, and the siphon is cutting.

The flow is still pretty lousy. I'm guessing it's my design. The first compartment will get decent flow, the rest gets what looks like 1/10 of the pipe capacity.