Small pump for upflow activated carbon and flow rate?

[kdx7214]

I'm working on a little DIY upflow carbon filter to polish tank water. Anyone have a recommendation for a small pump or what flow rate I should aim for? It's for a 75g DT with 40g sump.

 

[vpierce3]

I would start with a little 300gph pump with a valve on it to restrict the flow. You want the water to pass through the carbon without tumbling it. Important not to tumble, otherwise it will create dust particles that will coat your sump/tank.