SunSun HW-304B External Canister Filter

The SunSun HW-304B is an external canister filter that sits under the tank and pulls water down through its media before pumping it back up. It’s a 5-stage filter rated at 525 gallons per hour (2000 liters per hour), and SunSun says it’s good for tanks up to 150 gallons. The feature that sets it apart at this price is a built-in 9W UV sterilizer.

What the UV sterilizer does

Water passes a UV lamp on its way back to the tank. The light damages free-floating algae spores and bacteria, which is the main cause of green water. It won’t remove algae growing on glass or rock, and it doesn’t replace water changes, but it helps keep the water clear.

Space and setup

The canister measures about 11 x 11 x 17 inches, so measure the cabinet under your tank before ordering. It weighs about 14 pounds empty, more once it’s full of water and media. A few setup tips help avoid trouble:

• Seat the hose fittings carefully. Leaks on canisters usually come from fittings or the lid seal, so check them before you leave it running.
• Prime it fully. Fill the canister with water before starting, and let air work out of the lines.
• Use a drip tray or towel. Put something under it for the first few days, until you’re sure nothing drips.

Media and maintenance

Lay out the media so coarse sponges catch debris first and biological media sits after them. Rinse sponges in old tank water, not tap water, every few weeks. Replace the UV bulb when it no longer clears green water, and clean the quartz sleeve so the light gets through.

Who should look elsewhere

For a tank under 40 gallons, 525 GPH can create more current than fish like. The instructions are basic, so first-time canister owners may find a more polished brand easier, such as the Fluval 307 or the larger Fluval 407, though neither includes UV.