What Are the Benefits of a Sump for a Freshwater Aquarium?

The sump filter revolutionized the saltwater aquarium -- it was arguably one of the innovations that made complex hobby reefs possible. It started as a saltwater aquarium filter and has largely remained in that domain, though there's no real reason it can't work its magic for a freshwater tank.

  1. Out of Sight

    • One of the big benefits of the sump filter is aesthetic. In a sump filter, you drain water from the main aquarium into a sump, filter it and then pump it back to the main aquarium. Within the sump, you can hook in all of your unsightly aquarium equipment, like smaller filters, heaters and other gear. In most cases, people will hide the sump in a sturdy aquarium stand under the main tank. In terms of aquarium equipment, the only thing that shows is the drain to the sump and the return plumbing.

    Increased Water Volume

    • One of the big benefits of a sump filter is the increased water volume. A sump filter functionally increases the volume of the aquarium. Since most guidelines for stocking a fish tank are based on water volume, this means that you can safely fit more fish in your tank without taxing the filtration or risking the health of your fish. Keep in mind that this only applies to the biological filtration of your tank. Some aggressive fish need more space because they will attack others.

    Biological Filtration

    • Another benefit to the aquarium is the increase in biological filtration. Most people make their own sump filters, so there's tremendous variety in the specifics, but most sump filters include materials with a high surface-area-to-volume ratio to encourage biological filtration. These include things like bioballs, ceramic noodles, and filter floss. Biological filtration breaks down fish waste and is critical to the long-term health of your aquarium.

    Easy Water Changes

    • You can also set up your sump filter to make water changes easier. Some designs incorporate a spigot, allowing you to drain water with the twist of a valve. You can also install an extra water pump just for water changes. The sump filter allows you to make water changes without lowering the water level of the main tank and without freaking out the fish by running a siphon into the tank for your maintenance.