Simple sump design

[BMW Rider]

another question: my hang-on over flow does 600gph, my return pump is 2400gph, I should install a valve to lower the pump flow shouldn't I? It shouldn't return faster than the overflow right?

Yes, you need to reduce the output of the pump to what the overflow can handle. a 2400 gph pump seems a bit overkill for a 600 gph overflow. You can use a few options:

1. Just gate down the return to reduce the flow. This is kind of inefficient because you end up wasting the pumps energy for no good purpose other than creating heat.
2. Divert some of the flow back to the sump through a tee with valves to balance the flow. I did this on my FOWLR, and run the excess flow through some charcoal (the pump is pretty close to the flow rate of the overflow, so there isn't a lot of excess flow).
3. Get a pump that is better matched to the flow rate you desire for the sump. You can still set it up as above. The big pump could then be utilized for a closed loop to increase your water flow in the display tank. This would be my suggestion as a best solution.