The Benefits of an Aquarium Sump

Aquarium sump 101

What’s up Salt Nation, Jeff Hesketh here. Today I wanted to write about the aquarium sump. I got sumps on my mind… mostly because I’m picking up my custom sump (which I designed) this weekend. This is a large subject that doesn’t get a lot of attention so lets see what we can do to fix that.

The Aquarium Sump

An Aquarium Sump is nothing more than an aquarium or container placed (most often) below the display aquarium. This aquarium receives water from the display aquarium through plumbing which passes through filter socks, baffles, filter media, a protein skimmer, more baffles then returned to the display aquarium.

The Aquarium Sump

Most people new to the hobby try everything within their power to avoid installing a sump in their saltwater aquarium setup. The benefits of an aquarium sump far out weigh any of the disadvantages. All it takes is some additional planning to avoid them.

Sumps can also serve other purposes than for hiding equipment and adding water volume. Many aquarists design their sumps to be used as a trickle filter, an algal filter, or a refugium, as well as simply holding water and equipment.

The benefits of an aquarium sump:

  • Increased water volume.
  • Increased aerating in the water.
  • Providing a place for (and concealing) equipment.
  • Improved excess-ability for water changes.
  • Keeping the water level stable in the display tank.
  • Keeping the surface of the water free of debris.
  • Can be a safe haven for microfauna like copepods and amphipods

In-Depth look the Benefits of a Aquarium Sump

Increased water volume. Increasing the total water volume in a saltwater aquarium is beneficial because the more water within the system, the more stable the system becomes. Water temperature and chemistry will change more slowly in larger volumes of water, which makes it easier to keep the system within optimal parameters.

Increased aerating in the water. Aeration of the water will be better because of the water moving over the overflow, down the drain and splashing into the sump. This will help with gas exchange between the water and air. Increased dissolved oxygen is beneficial to fish and can also aid in avoiding Cyanobacteria outbreaks (red slime)

Providing a place for (and concealing) equipment. Having a sump installed on a system allows equipment, such as heaters, filters and skimmers, to remain hidden so that they don’t disturb the aesthetics of the display tank. Also, with a sump, it is generally not necessary to keep powerheads in your tank for circulation.

Improved excess-ability for water change. Sumps can also help make water changes a little easier. Water can be removed from the sump without lowering the water level in the display tank. Additionally, replacement water does not have to be lifted up or pumped into the display aquarium.

Keeping the water level stable in the display tank. A few factors will effect evaporation such as the size of the tank and the humidity of your house, I’v seen my water levels drop as much as an inch in one day in my larger aquariums. The return pump in your aquarium sump will keep the water level in the display aquarium constant. While the water level in the sump lowers due to the evaporation of water. Being located in your stand below your aquarium, affords you the use of an auto top to battle evaporation and improve the stability o the aquarium.

Keeping the surface of the water free of debris. The overflow is the mechanism for removing water from the main tank. It pulls water from the surface then it flow into the sump. This can aid in the removal of debris from the surface of the water in the display aquarium. I’ve experienced this with my first saltwater aquarium which did not have a sump and it can be extremely unsightly.

Can be a safe haven for microfauna like copepods and amphipods. Within the reef aquarium hobby, a refugium refers to a chamber inside your sump (or in a separate container) where macroalgae, rubble rock and fine sand or mud is housed to provide biological filtration. In addition to the filtration benefits, refugiums are enormously beneficial to reef tanks. Aquarium provide a safe haven for microorganisms, like copepods. This allows them to grow and reproduce so they can feed livestock inside your display aquarium.


I hope this article has given you a better understanding of the benefits of an aquarium sump. Also, why they are so important to saltwater aquariums. This is just the first of many aquarium sump article to come. For more reading follow the link.

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