You will want a skimmer for your sump. Only necessary thing is a return pump. Your going to need an overflow box as well. I highly suggest drilling your tank and installing overflow bulkhead and return bulkhead alone with box.
Hang on the back overflows can be unreliable cause your sump to drain and a big mess on the floor. Power outages also can cause problems with hang on overflows.
29g Mixed Reef, 150w 14k Phoenix MH w/ Moonlights, Reef Octopus BH1000 HOB Skimmer, Ecotech Vortech MP10es, ReefKeeper Lite (Plus), PH Probe, Temp Probe, ATO, Carbon/GFO Reactor.