The Best Internal Aquarium Filters

By Shirlie Sharpe

Updated 11/11/19

Man inspecting fish tank

vgajic / Getty Images

Fully submersible (internal) filters are perfect if you have an area in your aquarium where water flow needs to be increased. They are effective if your tank carries a high bioload and is in need of supplemental filtering. Low-water habitats, such as paludariums, are also ideal spaces for an internal filter. The general rule of thumb is to use an internal aquarium filter on small tanks under 20 gallons. Once you know that you need one of these filters, how can you find the best internal aquarium filter?

How Internal Aquarium Filters Work

Internal filters must be completely submerged in the water to work correctly. For most, the airline must be connected to the inlet of the filter. The air is driven by a pump that is situated outside of the aquarium. Air is pumped into the filter and moves through it. Then it is dispersed on the water surface. The air bubbles create much-needed movement in the water that allows it to filter the liquid throughout the entire tank.

The filter can be affixed with suction cups to the tank walls, or placed on the ground of the tank. Most people place it in a corner of the tank, and most internal filters come with suction cups, so you may not have to purchase them separately.

Benefits of Internal Tank Filters

There are a few benefits of using internal filters, though not every aquarium requires one. Instead of being kept in a cabinet or hanging on the back of the tank, the placement of an internal aquarium filter allows you to put your aquarium against a wall. Internal aquarium filters are also relatively inexpensive, easy to install, quiet, and they do not require a ton of maintenance.

Choosing an Internal Aquarium Filter

When you know more about the species that will live in the aquarium, then you can base your choice of filter on those requirements. There are a few internal filters that offer superior performance.

  • 01 of 02

    Duetto

    Under Gravel Filter

    PriceGrabber

    What separates this internal filter from others is an adjustable aeration feature that thoroughly mixes air with the water. This gives it an effective gas exchange. Two output adapters allow for horizontal or vertical placement in the tank, so it offers some versatility.

  • 02 of 02

    Fluval

    Fluval

     Photo from Amazon

    This small but powerful filter allows for a choice of filter media. It also rarely clogs and is very affordable. Like all internal filters, the primary downside is that cleaning is cumbersome because it must be removed from the aquarium. Being able to choose different media is a perk because you can use different brands, or choose less-expensive filters.