A freshwater sump filter is nothing more than a tank that contains all your filtration, media, water pumps and heater. To view other types of filters, visit my previous article “Aquarium Filters“. Generally, we place a sump filter beneath the aquarium. It is made from the same materials that are required when building an aquarium. Traditionally, sump filters were used in marine tanks where good water quality is essential. These days as freshwater tanks are getting better and larger. Fishkeepers have started keeping larger fish and sump filters are getting popular because of it’s excellent, effective and efficient filtration they offer.

When it comes to submersed sump it all about baffle. There are basically walls inside sump that directs water. Size of the freshwater sump filter should be large enough to accommodate media equipment and additional water that drains when the power goes out.

Since sumps are customizable there are few designs of them. Some of them being a little more complicated than other, which will also involve drilling hole in the tank. Thesedays, you can purchase a fish tank that is sump installation ready.

The main advantage of having a sump system is that it increases water volume in the system. Making it more stable and less prone to fluctuations of pH level. And also the water movement main tank and the sump helps with the gas interchange between air and tanks water, increased dissolved oxygen is good for fish. The most important reason to have a freshwater sump filter is that it separates all of the technical fish tank’s equipment from the display tank. Your main tank is the display tank. The tank hidden beneath the display tank is the sump.

Keeping a freshwater sump filter system makes your life easier and makes your life in the tank happier too. Because if you keep a sump you can go with bigger filtration system with lots of media, big mechanical filtration, lots of biological media. And whatever you want to keep in the sump like temperature sensors, chemical sensors, UV lights, and so on.

freshwater sump filter

Some of the advantages of sump over other filter are:


Introducing sump system in your aquarium system increases flexibility in terms of use of media like ceramics rings, foam beads, fluidized moving bed (K1 media). Accommodating various accessories heater, sterilizers, and other accessories.


Other filters like HOB, power filters, canister filter can handle only a set volume of water, whereas sump system is customizable you can build as big as you require.

Stock levels

Introducing sump in your system increase your water volume. The tank connected to sump can be stocked above normal limits without overstocking fish.


Compared to other filter systems, a freshwater sump filter is much easier to maintain. It helps in maintaining water quality in a larger tank is easier than in the small one. It makes water quality stable.