How to Stop an Aquarium Refugium From Overflowing

A gravity drain can keep your refugium from overflowing.

A refugium is a small fish tank that is attached to the main fish tank. Such add-ons are typically used to house delicate aquatic species, such as baby fish or shrimp, that would be chased or eaten in the larger tank. A refugium shares its water with the main tank, with a water pump cycling water between the two, and it may overflow if not set up properly. Learn how to stop a refugium from overflowing to keep your floor dry and your fish safe.

Things You'll Need

• 1/2-inch-wide PVC pipe (varying lengths)
• 2 PVC elbow joints
• Saw

Instructions

1. Remove the fish or invertebrate living in the refugium. Working on the refugium may disturb the tank's substrate and considerably stress its fragile residents. Place the refugium's residents in a holding tank, or float them in a large plastic bag in the main tank.

2. Build a gravity drain. The drain uses the force of gravity to draw water from the refugium back into the main tank. Use the saw and cut a piece of PVC pipe that reaches from the top of the refugium's tank rim to just above the surface of the water in the main tank.

3. Cut a shorter piece of PVC pipe. The piece should be long enough to stretch from the top of the long PVC pipe over the refugium's rim. Connect the short piece to the long piece with a PVC elbow joint so that it resembles an inverted L, with the short end hovering over the refugium.

4. Saw an even shorter piece of PVC pipe. It should measure from the tip of the short end of the inverted L to just below the surface level of the refugium's water. Connect the shorter piece to the inverted L with the last PVC elbow joint. The contraption should now resemble an inverted J, with the short end of the pipe in the refugium and the long end just above the water level in the main tank.

5. Prime the gravity drain. Remove the pipe from the tanks and fill with water. Use your thumbs on each end to keep the water inside the pipe. Place back into the main tank and refugium, and release your thumbs. Gravity will siphon water from the refugium into the main tank.

6. Adjust the pump power that is responsible for pumping water from the main tank into the refugium. Raise or lower the pumping power so that the pump keeps up with the emptying rate of the gravity drain. The refugium's water will now circulate safely without risk of overflowing.

7. Place the refugium's fish or invertebrate back into the small tank.

Tips & Warnings

• Use silicone glue to attach the PVC pipes permanently to your tank if you are worried that you may accidentally knock the gravity drain out of the refugium.

References

• Tropical Fish: Caring For Your Pet; Nick Fletcher; 2001

Resources

• Examples of a Refugium