Plumbing

Just picked up my new 80g tank. Never had to use a sump before so I was wondering what my max gph should be? Im going with an Eheim so would it be better to go with a 1250 (317gph) or do a 1260 (635gph) with a ball valve in between?

Ive heard that you want a lower gph for your return to let the skimmer work right? The tank will have mostly LPS and fish.