Return pump goes into your sump and pumps the water from below in the sump to your tank. BUT you would have to have a way of getting the water from your tank down below into your sump. You could drill the tank OR get a hangon back overflow.
The sump is useful to put all your equipment like heaters and it will increase the amount of water you have in your system which helps make it easier to take care. More water volume the better...
180g Reef - 60g Rimless Reef -90G FOWLR- 125g Malawi Cichlids- 40b REEF- 34g Fresh Planted-working on- 20L FOWLR- working on
I have a mix of many different saltwater fish amongst my tanks, but I love my Tangs most of all.