The Beginner's Guide to Submersible Fish Tank Filters

The Benefits of Submersible Fish Tank Filters

Submersible fish tank filters are a great option for aquariums for a number of reasons. They are quieter than external filters since they are under the water. Submersible filters don’t require additional space outside the aquarium. They can be hidden by blending them into the aquarium decorations.

Submersible fish tank filters are cheaper compared to external filters. If you are on a budget or short on space, such a filter may make sense.

Types of Submersible Fish Tank Filters

Submersible fish tank filters can be broadly categorized into two types based on their functions.

Pump-Powered Filters

Pump-powered submersible fish tank filters are commonly found in small aquariums. The device consists of a small canister with a pump along with sponges and filtration media (chemical and biological). The pump is generally located at the top or bottom of the filter. It sucks water through the sponges, trapping debris and waste for mechanical filtration, and then pushes it into the compartments with biological and chemical filtration media. Smaller and older models may only have a single compartment for filtration media.

Pump-powered submersible fish tank filters have a valve that allows you to adjust the water’s flow rate. Many of them have integrated aeration devices for blowing bubbles into the water.

Air-Powered Filters

Air-powered submersible fish tank filters used to be popular but are less common nowadays. They are beneficial when the water current in an aquarium must be kept to a minimum.

Their gentle flow ensures that small fish are not sucked into the filter. Air-powered filters don’t have an integrated pump.

Instead, they are used with an aquarium air pump. You connect the filter to a pump for cleaning the water. The flow rate of air-powered submersible fish tank filters will depend on the air pump’s pressure. They employ thinner foams or sponges for filtration. Compartments for additional filtration media are rarely present in them.

As a result, air-powered filters have a poorer efficiency and don’t clean a tank as well as pump-powered filters.

The Downsides of Submersible Fish Tank Filters

Submersible fish tank filters are suitable for small aquariums. They have a compact size and must be installed internally. This limits the amount of media that can be added to them as compared to external filters. Therefore, they require frequent maintenance, as the filtration media will get saturated quicker due to its limited quantity.

Therefore, they are more suitable for aquariums with hardy fish species. They will do well in sparsely populated aquariums but may not be adequate when keeping a lot of fish in the tank.

Choosing a Submersible Fish Tank Filter

Submersible fish tank filters are available from different manufacturers and come in various capacities. There are a few considerations to keep in mind when choosing a model.

Capacity/Size of Fish Tank

The first thing to consider when choosing a submersible fish tank filter is the size of your aquarium. These devices have different flow rates, which is stated in gallons per hour (GPH). Select a submersible fish tank filter that provides an adequate flow rate for your tank’s capacity.

Don't shortcut this consideration! Using a smaller filter for a larger tank will degrade the water quality and shorten the device’s lifespan.

Filtration Media

Submersible fish tank filters may have one or more types of filtration media in addition to a foam or sponge. Some of them only have a compartment for biological filtration media, while others also accommodate chemical media. A few premium filters also include activated charcoal to remove impurities and odor.

As a general rule, submersible fish tank filters with more filtration media clean water better, but that also increases the price.