Return to tank?

[mosssw]

Can I fit PVC to my return and run them down in the tak for better flow or do they need to stay at the top with the "jets" that came with it?

[Playa-1]

For a closed loop system it would potentially be acceptable to do what your describing. But , if it just the typical sump/fuge return pump then you would be asking for problems. A power outage could potentially cause a major draining event of your display onto your floor if your not careful.