How to Set Up a Refugium on an Existing Canister Filter System

Add a refugium to an existing tank to give yourself more options and water capacity.

A refugium is a secondary tank that sits outside of your main aquarium. These outside tanks are useful for storing filtering equipment, growing food sources like algae and plankton, and acting as "refuges" for animals that can't survive the environment of the main tank. Because a refugium generally shares a water supply with the main tank, it can also share the filter and pump system. To use your existing system with the addition of a refugium, simply make a couple of modifications to the setup.

Things You'll Need

• Secondary tank
• Power drill
• Plastic hose (3 pieces)
• Sealant
• Secondary pump

Instructions

1. Organize your setup. You will need some sort of secondary tank to your main tank, with room for both tanks to sit evenly and plastic hosing to run between the tanks without stretching or kinking.

2. Empty both tanks before you start to ensure that you're working in a dry, safe environment. This is a good opportunity to empty and clean your existing canister filter. Do not eliminate any of the biological media from your filter system, as it's an important part of the filtration process. This is also an ideal time to replace any filters or damaged parts on the system, and to give it a thorough rinse. Set both the main tank and refugium in their desired locations now, while they're empty.

3. Use the power drill to drill two holes in the side or back of the larger aquarium, as close to the top as possible. These holes will house the plastic tubes, which will be responsible for circulating water between the main tank and refugium. The holes should be slightly larger in diameter than your plastic hose, which is available at all pet and aquarium supply shops.

4. Insert the ends of two of the pieces of hose into the holes in the main aquarium. Make sure that the hoses can reach from the holes to the bottom of the refugium without kinking or pulling out. Once you've confirmed that the hoses are long enough, use the sealant around the holes in the main tank to seal the tubes in and prevent leaks.

5. Transfer your canister filter system closer to the refugium, where it will now sit. Set your new pump up in the refugium, per manufacturer directions. Since your canister system sits outside the tanks, this second pump is necessary for pumping water from the refugium back into the main tank. Attach one of the hoses from the main tank to the sucking function of the canister system. Attach the third (free) piece of plastic tubing to the pumping function of the canister system, and secure it to the inside of the refugium. Finally, attach the second hose from the main tank to the pumping function of the secondary pump inside the refugium. This system will now pull water from the main tank, pass it through the canister filtration system, pump it into the refugium, and then pump it back into the main tank.

6. Fill the main tank with water, fill the refugium halfway, and turn the pump and filter on. Monitor the setup for at least an hour to watch for leaks and/or flooding. Be aware that interruptions in power or turning the filter on and off could cause disruptions in your water circulation.

Tips & Warnings

• Use a refugium as a holding tank for young fish until they're old enough to take care of themselves in the main fish tank.

• Build a refugium out of an old, unused fish tank.

• Running your filter and pump while they're dry will burn out the engines and destroy them.

References

• Melev's Reef: How Does a Sump Work?
• Brett's Reef: How a Saltwater Aquarium Sump Works
• Fish Tank: What Is a Refugium?