would this work?

[Quagmire]

I dont think you'll have enough flow.3x 20g turn over is only 60g.So thats just over 1x turn over in your main tank.Plus your canister filter.Dont know what you plan on keeping,but rule of thumb for salt water is 10x turn over.And for a reef tank anywhere from 30x-60x depending on the corals your keeping.As far as your sump goes,the turn over would be fine,but expect to syphon the crap that will settle on the bottom.

[spikehs]

oh thats just for through my sump. I have 2 tunze nano streams so I should have ~ 30x turnover total... i really want a slower flow through the sump so its quieter...

[Quagmire]

In that case,just read the last sentance