When it comes to return pumps the "standard" seems to be 10x turnover so something around 300gph would work, but with that being said you can always get away with a little less or a little more. Depending on your plumbing at the bare minimum something like a Sicce Syncra 1.5 would work. From there you can go to a larger size if you are going to be running any equipment off that pump. DC pumps are always nice because you can always turn up or turn down the power.