Smallest Hang on Back Filter for Small Fish Tanks

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So you have a small fish tank (5-10 gallons) and looking for the smallest hang on back filter. In this article, I will tell you which is the best small hang on back filter, and why to use it.

Hang on back filters are great for small aquariums, because they are very compact, don’t take up space in your already small fish tank, are easy to clean and can filter the water very efficiently.

In my opinion the AquaClear 20 available on Amazon is the best smallest hang on back filter. This HOB filter is suitable for small aquariums between 5 and 20 gallons in size. I use and highly recommend the AquaClear hang on back filter.

That said, let’s see what are the benefits and downsides of using the Aqua Clear hang on back filter on a small aquarium.

Aqua Clear Hang on Back Filter Review

The Aqua Clear HOB filter has 5 different models. The smallest one is recommended for 5-20 gallons aquariums, while the biggest one is suitable for 60-110 gallons.

I don’t recommend using a hang-on back filter on aquariums that are bigger than 50 gallons. On bigger tanks, you can use a HOB filter as a secondary filter, but you should not rely on it entirely.

For small aquariums, though, the Aqua Clear hang-on-back filter is a great choice.

The output of the AquaClear 20 is up to 80 GPH and has a very low operation cost of 6 Watts.

I like this filter, because it is easy to setup and easy to clean. The filter comes with a 3-strage filtration and contains a lot of filter media.

The sponge filter, which is placed to the bottom of the filter, is responsible for filtering out debris and particles from the water. The sponge also helps in biological filtration.

The activated carbon acts as chemical filtration, which will remove toxins (not ammonia), heavy metals and discoloration from the water.

The ceramic rings, which are placed at the top of the filter basket, provide huge surface area for the beneficial bacteria, which will break down ammonia and nitrites and turn them into nitrates.

Another thing I like about this filter is the adjustable flow rate. The small nob on the top of the filter, allows you to turn up or down the flow rate, as you need.

This filter is very quiet. You won’t hear any humming or vibrating sounds. The sound of the falling water can be annoying for some people, but this can be fixed with topping up the water level to the outflow of the filter.

Anyways, here is a quick video on how to setup the AquaClear 20 hang on back filter:

How to Maintain the Aqua Clear HOB Filter?

The maintenance of HOB filters in general is very easy. The Aqua Clear is also very easy to maintain and clean.

Always unplug the filter, when doing any cleaning.

First, remove the cover then take out the filter basket, which holds the filter media. Put the filter media into a bucket that contains aquarium water. Keep the BioMax ceramic rings in the aquarium water until you are done with the filter cleaning. This way, you will prevent the dying of beneficial bacteria.

Rinse the sponge filter under tap water or in aquarium water.

You can rinse the activated carbon bag as well the ceramic rings in aquarium water to get rid of any debris that has built up in the bag. Do NOT wash these media using tap water!

After this, clean the impeller with a soft brush using lukewarm water and dump out the dirty water from the filter case.

Time to time it is good to clean the intake tube as well, though it is not essential to clean it every time you maintain the filter.

After you are done cleaning, assemble the filter, put the filter media back in the right order (sponge on the bottom, active carbon in middle and ceramic rings on the top) and plug back the filter.

The Aqua Clear filter will self-prime and will start running again in just a few seconds.

The cleaning of the Aqua Clear filter should not take more than 10 minutes. I’m usually done within 5 minutes with the cleaning. It is very easy.

When Should You Replace Filter Media?

The manufacturer says that you should replace the filter foam every two months. The activated carbon should be replaced monthly, while the BioMax ceramic rings every three months.

In my opinion, you should never replace the sponge filter and the ceramic rings. In fact, replacing the biological filter media in the filter is a very bad idea. By removing the old bio media, you will remove all the beneficial bacteria from your fish tank, which are essential to turn the highly toxic ammonia and nitrites into nitrates.

Activated carbon media, though, should be changed time to time, because it can become depleted after a while. Though, in a small aquarium, where you don’t add many chemicals, just feed your fish and do weekly water changes, activated carbon can last for a very long time (up to 1 year).

So, don’t spend money on replacing established filter media, just do regular filter maintenance to keep the bio media clean of debris.

Can You Use the Aqua Clear Hang on Filter in Fry Tank?

The Aqua Clear filter is ideal for tanks, where you have guppy fry. The intake tube has a grid, which prevents small fish to be sucked up into the filter.

Though, if you want to be 100% sure, that your guppy fry will not get into the filter, you can place a small sponge on the intake pipe.

Just remember to clean this sponge weekly, or when you do water change, because it will reduce the performance of the filter if the debris builds up on it.


Certainly, there are other good small hang on back filters out there, but I really like the AquaClear.

If you have any questions regarding this product or filtration, please leave a comment below or send me an email. If you have any experience with this product, please also leave a comment.

Hope, this guide has helped you find the smallest hang on back filter for your aquarium.

Updated: January 9, 2022
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