nope. Your overflow will do fine. I would go with a mag drive 3 as the return and your skimmer is with the sump so it will just re skim the water which is good. Those skimmers are HUGE just make sure you baffle the skimmer before the refugium. That way your refugium doesnt get a lot of detritus. If possible I would have jst a sump and a refugium seperate...That would be best. then you wouldnt have to baffle a tank. maybe a ten gallon refugium piped to a 15 gallon sump.