3 Best Internal Filters For Aquariums + How To Choose

Image of an aquarium with internal filter

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Filtration plays an important role in creating a hospitable environment for the inhabitants of an aquarium. A good filter helps maintain good water quality, which helps aquatic pets and plants stay healthy and happy. Internal filters are ideal for small to medium fish tanks with low filtration needs. They clean the aquarium water by removing toxins and make your fish tank a safe and healthy living environment. So, what are the best internal filters for aquariums?

The best internal filters for aquariums are the ones that are compact and efficient. They operate quietly, with the flow rate being optimized for space. They are also easy to clean and maintain. Such internal filters use various filter media to optimize the filtration process of the aquarium water.

Let’s talk about these internal filters in detail now.

3 Best Internal Filters For Aquariums

Given below are the top three internal filters that you can get for your aquarium today.

  • Provides effective and thorough biological and chemical filtration, creating superior aquarium water environment
  • Activated carbon and fine filter foam trap debris and fish waste, absorb odors
  • Enable to generate abundant air bubbles and water flow, optimal for oxygen supplement and water circulation of aquarium
  • Equipped with adjustable air regulator that distributes a gentle flow of water, making it safe for delicate fish or shrimp
  • Quickly assembles and disassembles, comes with four suction cups for secure in-tank installation, suitable for both freshwater and saltwater tanks
  • Fully submersible aquarium filter quietly delivers 175 gallons per hour of crystal clear water for your fresh or marine aquarium from 20 to 50 gallons in size.
  • Activated carbon cartridge removes harmful chemicals, toxins, odors, discoloration, and other contaminants for your aquarium.
  • Internal sponge optimizes colonization of beneficial aerobic bacteria. Large capacity aquarium filter cup allows you to choose your own filter medium.
  • Pump head with adjustable and directional water flow. Cascade internal filters provide better filtration; physical, chemical and biological while also aerating water.
  • Spray bar option allows you to distribute water evenly helping aerate your tank. Fish tank filter can be placed horizontally and is easily hidden.
  • age range description: All Life Stages
  • Use as a primary filter for smaller aquariums, or supplementary filter for larger aquariums
  • Sleek design with easy grip water control panel and redesigned media cartridge to trap more debris
  • Convenient flip-top lid allows for quick and easy access to filter cartridge for maintenance or replacement
  • Position horizontally for shallow tanks, larger tanks with low water levels, or to create a decorative waterfall feature or vertically against aquarium wall to create currents or customized flow patterns
  • Designed for freshwater, saltwater and reptile environments up to 30 gallons

Recommended Further Reading:

How Do Aquarium Filters Work?

We use fish tanks to keep fish and other aquatic creatures. These organisms expel natural waste into the water around them.

Leftover food, plant material, and other debris also form aquarium waste. All these different types of waste pollute tank water.

Over time, they release toxins into the water. These pollutants make the water cloudy and smelly. If you leave it unchecked, this waste can cause various diseases and affect the health and well-being of the tank inhabitants.

A filter will trap this waste and remove it. This equipment uses mechanical, biological, or chemical filter media for this purpose.

Mechanical filters use sponges, wool, or floss to trap waste. They hold on to it until you manually clean them and eliminate the trapped waste.

Biological filters have nitrifying bacteria that convert toxins like ammonia and nitrites in the waste into less harmful nitrates. Once the helpful bacteria establish a colony in the tank, they form a self-cleaning system that preserves the water quality on an ongoing basis.

Chemical filters use carbon or charcoal to absorb impurities from the water. They remove organic pollutants and make the water clear and odor-free.

Now, there are numerous types of filters in the market. We can broadly classify them into internal and external filters.

Internal Filters Vs. External Filters

As the name suggests, internal filters sit inside an aquarium while external filters are kept outside the tank.

Internal filters are smaller than external filters. They are suitable for small to medium fish tanks with low filtration needs. These filters work only when they are completely submerged in the water.

Most internal filters use a combination of mechanical and biological filtration for efficient operation. You will occasionally have to remove the filtration media and clean it before it becomes fully clogged.

Tanks with higher filtration needs need large external filters. They are more powerful than internal filters. These filters suck the water out of the tank through tubes. After cleaning the water, they pump it back into the tank.

External filters need more space. So, you will have to place them beside or under the fish tank.

These filters hold more filter media. Hence, they require less frequent cleaning compared to internal aquarium filters. Nonetheless, cleaning an external filter usually takes more effort.

Related Further Reading:

Are Internal Aquarium Filters Good?

Internal filters are suitable for small to medium tanks with a low bioload. The main advantage of using an internal filter is that it has a small footprint. Hence, it does not occupy much space.

It is also not as expensive as an external filter. You can easily install it, and it works quietly without disturbing the tank inhabitants.

Nevertheless, internal aquarium filters need frequent maintenance. They can hold only small amounts of filter media.

The sponges and filter wool get clogged with waste in a short time. So, you will have to clean the filter media frequently to keep it functional.

If you do not get rid of the gunk that builds up, the efficiency of the filter gets affected. It can make the water in the tank cloudy.

Toxins that build up over time will make the environment unsafe. Slow running filters will also affect the oxygen level of the tank.

When you use an internal filter, you should clean the filter media every few weeks. You can get rid of the trapped waste by rinsing the sponges in the old tank water.

Never use tap water for cleaning the sponges. Tap water will kill the friendly bacteria in the sponges and disrupt the natural nitrogen cycle of an established tank.

The more filter media a filter contains, the longer you can go without cleaning it. External filters are larger than internal filters because they carry large sponges and other media. Due to this, you can go for a long time without cleaning these filters.

Internal filters are also not suitable for large tanks with plenty of large fish. You will also need a powerful filter if you keep messy fish like goldfish and cichlids. These fish produce more waste. Small internal filters cannot hold up to their filtration requirements.

Where Should Internal Aquarium Filters Be Placed?

You must place internal aquarium filters inside the fish tank. This equipment will filter the water while remaining submerged in the water. Most filters have suction cups to attach to a surface.

Corner box filters can be kept in the rear corner of the tank, with their outlet below the water surface. You can place it at the bottom of the tank or attach it to a wall.

These filters automatically draw water in through the bottom and pass it through the filter medium. The debris is caught in the medium.

If there is a biological filter medium, it converts the toxic ammonia and nitrites in the waste into less harmful nitrates. The filter will then return the cleaned and oxygenated water into the tank.

Sponge filters have a U-shaped tube to pull water through a sponge-like material. Beneficial bacteria are present in the sponge. They perform biological filtration before returning the water to the tank.

Older internal filters used to be under gravel models. These filters would occupy the base of the tank. These filters would filter the water flowing through the substrate. They used mechanical and biological filtration to clean the water. Due to the higher maintenance involved, these filters are no longer popular.

Interesting Further Reading:

Best Internal Filters For 20 Gallon Aquariums

Here are some of the best internal filters for 20-gallon fish tanks.

Hang-on external filters are generally recommended for large aquariums. However, you can also make it work with an internal filter.

If you have a 20-gallon aquarium, it is best to choose a filter that is designed for a bigger tank. Most manufacturers rate their filters without testing with filter media. So, it is best to play it safe by using an oversized filter that will compensate for any extra waste that your fish produce.

A filter with a higher rating will help the aquarium sustain and prevent fish diseases and algae growth, even if the bioload is high.

When choosing an underwater filter, pick one that is designed for 40-gallon fish tanks, and you should be safe.

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