How to Start an Aquarium Overflow

Aquarium overflows pull water from your tank, allowing you to gravity feed the water down to a sump or refugium. If you did not have an overflow and were just using a siphon hose down to the sump, the sump could be flooded during a power outage. The water would continue to be pulled from the tank through the siphon but no water would be returned to the tank without electricity. Additionally, the aquarium could overflow once the power came back on and the return pump began working again because the siphon tube would have lost its prime. By having a double reservoir, the siphon action merely stops until the water level is returned to normal.

Things You'll Need

Airline tubing
Cup
2 rubber O-rings

Instructions

- 1
  Put a rubber O-ring on the drain connection. Insert the drain connection into the bottom of the overflow. Place another rubber O-ring on the drain connector on the inside of the overflow. Hand-screw the connector nut onto the connector inside the overflow, securing the two parts together.
- 2
  Slip the drain tube over the connector, pushing the drain tubing until it fits tightly. Check that the other end of the drain tube is still in your sump or refugium.
- 3
  Hang the overflow on the side of the tank. Adjust the side screws so the overflow hangs parallel with the side of the tank.
- 4
  Adjust the height of the overflow. The front edge should be just below the water level in the tank.
- 5
  Fill the chamber outside the tank that is closest to the aquarium with tank water.
- 6
  Insert an airline tube all the way to the top of the U-tube water connector or attach it to the siphon port of the weir depending on the type of overflow you have.
- 7
  Siphon the air out of the tube or weir channel by sucking on the airline.
- 8
  Once the air is sucked out of the channel or tube the overflow is primed and will flow on its own. Slip the airline out of the overflow tube or weir channel without breaking the prime.