Hello! Ive just got my new system up and running and your seeing my plumping in the middle of a rework. Before I cut to many pipes and give myself a bigger headache I thought I'd ask the community to help verify what might be going on and ensure I am solving the problem in the right way.

The system can be seen here: http://imgur.com/a/kU75t

Where I am currently at: I Have a sump tank with a single pump in it pumping upwards. This splits in 3 places - about 25% up to a return back into the sump tank, about 75% up it connects over to the plumping that feeds the grow bed. Then at the top it dumps into the fish tank. The fish tank drains from a gravity drain back directly to the sump, keeping the water level in the fish tank constant. The 3 grow beds are all flood/drain systems setup with a bell siphon, all working correctly.

My issue: Over time the water coming out at the top of the pipe, into the fish tank loses power and eventually stops. This means no water making it to the fish and is obviously a bad thing. If I stop/Start the pump, plenty of water making it to the fish, good power, etc. I assume this is because I have bleeds located below this point and over time gravity wins and takes all the flow into this pipes instead.

My idea to fix: I am guessing that I need to run all piping to the maximum high (top of fish tank) then T from there and have it feed down to the grow beds and seperately into the fish tank, that way 100% of the water makes it to the maximum height and is then just forked to its ultimate path.

Anything else that can cause this? Im assuming this is due to the waterlevel fluctuating in the lower sump tank so the head heigh is variable. When the sump is very low (when the top tanks are all about to drain) the pump has to work harder to push another foot or two upwards which results in lower flow to the top? Any way to work around this? Am I misunderstanding the problem?

Thanks!