Best Filter for 20 Gallon Tank 2021

Cleaning a fish tank can be a hassle if you have to do it manually all the time. This is why the tank filter was invented to keep you from doing that same task all over again.

However, it is worth noting that not all tanks and filters go together – they have size requirements that you may want to consider.

Why so? This is because tanks with small fish might not benefit from a filter that is too powerful. For example, Betta fish could be blown away or sucked in if they have a too-powerful filter! In other cases, a small tank filter could also be too weak to clean up your tank.

This is why you may want to look for the best filter for 20 gallon tank. You’re in luck because in this article, we compiled some filters for 20 gallon tank reviews to help you out in choosing.

Top 5 Best Filter for 20 Gallon Tank

Here are some suggested picks of ours for an ideal filter for 20 gal aquarium:

Aquaneat Aquarium Bio Sponge Filter

We picked this aquarium sponge filter due to its ease of setup and cleaning. It can be easily installed into any airline and combined with your tank-appropriate air pump and it is ready to go.

The filter can be used for small fish such as the dwarf cichlid, guppy, betta, killifish, and even tanks that have babies to avoid powerful sucking.

In the same way, you can also use it for shrimp tanks other than fish. The filter measures 4.5 x 8 inches and this makes it not so much obtrusive to your tank. The sponge filter does both mechanical and biological filtration.

Things We Liked

• Easy to clean
• Simple to install
• Can work well with small fish and babies
• Can also be used in shrimp tanks
• Mechanical and biological filtration

Things We Didn’t Like

• Doesn’t come with a proper manual

Penn Plax Premium Under Gravel Filter System

If you want an under-gravel filter, this one can be a good choice, since it is also rated for 20-gallon tanks. It helps to lessen the filtration process for your other existing filters due to the fact that it is able to make both biological and chemical filtration in one go. Just lay down this under-gravel filter and you’re all set.

It comes with its own set of air stones, lifting tubes (you can adjust them), filter cartridges, and even filter plates for you to use and enjoy for your fish.

All you need to do to set it up is to lay down the filter mat and then attach the lift tubes and filter plates. Then, you can connect your existing air pump to it. The mat measures 22.5 x 11.5 inches.

Things We Liked

• Low profile design
• Can work well with existing plants
• Nearly hassle-free and minimal maintenance
• Easy to install

Things We Didn’t Like

• May not be suitable for colored gravel due to possible fish kill

Aquaneat Large Air Pump Sponge Filter

Yet another sponge filter, this one comes with various accessories that you can easily install to any 20-gallon tank. It is easy to clean and install to any airline unit and has a total of 10 layers for its infusion chamber.

The size of the sponge filter set is most likely good for small fish such as guppies and Betta.

Measuring 6.5 x 2.4 x 9.5 inches, this filter set comes with airline tubing, a tee, a control valve, 4 suction cups, a non-return check valve, and the filter itself. You only need to clean it up every 2 to 4 weeks.

Things We Liked

• Not very obtrusive to fish in the tank
• Easy to set up
• Includes all the materials you need to set it up
• Can also be used in much smaller fish tanks

Things We Didn’t Like

• Doesn’t come with a proper manual

Aqueon QuietFlow Filter Cartridge

This medium filter cartridge comes with a total of 3 in the pack and can fit well in most 20-gallon tanks (and even 10-gallon tanks).

It is made with activated carbon that can help to clean the water inside your fish tank. You only need to change this filter cartridge every 4 to 6 weeks.

The filter media is very easy to install and can fit into most bottom key slots of existing filters. It can be great for those who are keeping goldfish as pets.

Things We Liked

• Helps reduce buildup on existing filter pumps
• Great for goldfish keepers
• Easy to install
• Ideal for those with Aqueon filters

Things We Didn’t Like

• Not as powerful as other filters

Aquapapa Bio Sponge Filter

As a set of 3 filters in one pack, this one provides both mechanical and biological filtration so it can be quite powerful for most 20-gallon tanks.

It doesn’t trap fish due to the design so it may be good for those who are keeping guppies, Betta fish, and even breeding fish.

Like most sponge filters, this one can give your tank more benefits if you use it in old tank water so that it will not kill the good bacteria for your fish. It doesn’t require an air stone and works in a gentle way for most small fish.

Things We Liked

• Has a good pressure for small fish
• Comes in 3 filter sponges
• Good even for low water level tanks
• Safe for breeding fish

Things We Didn’t Like

• May have a bit of bad smell at first

Frequently Asked Questions

Here are things you may want to consider before you buy the best filter for 20 gallon tank for your needs:

How do I choose the best filter for 20-gallon tank?

In order to choose an ideal tank filter for that size, you may want to look for the following:

1. Filter technology used. There are different kinds of fish tank filters (listed below) so you should choose the appropriate one for your tank needs.
2. Is it bulky or light? Filters that are too bulky may take away the room from the fish. Active fish may need a lot of room to swim around so that they don’t feel awkward.
3. The brand of the filter. Most fish tank filters that are of reputable brands can be significantly better than those that are made by generic brands.
4. Ease of maintenance. You may want to consider a fish tank filter that is easy to maintain and to clean. However, keep in mind that most filters require you to keep at least some of the beneficial bacteria for the fish to grow and thrive properly.

What are the different kinds of fish tank filters?

Depending on the filter type you have, you can achieve a different result for your fish tank. Here are some of the most common types of fish tank filters:

1. Air-driven sponge filters. These are the most common and they can be connected to any airline tank. Make sure that the filter pump is not very harsh to small fish.
2. Under-gravel filters. They can be situated in your tank bottom and they work well for being a secondary filter underneath the gravel or substrate.
3. Canister filters. These ones are more suitable for larger tanks so most 20-gallon tanks don’t use them.
4. Power filters. These ones can sit at the back of the tank and can be loaded with filter media. The filter media that you can use here include those carbon pads, which you can change every 4 weeks or so.
5. Wet/dry filters. If you have a saltwater aquarium then this may be an ideal filter for you. It helps to increase the levels of beneficial bacteria for your fish to thrive in a good environment.

How do I decide on fish to keep in a 20-gallon tank?

If you don’t know what fish to keep, here are some things you should research about for your tank and the fish:

1. Size. Small fish do better in small tanks and should not be mixed with large fish such as the tropical ones.
2. Social behavior. Some fish prefer to be alone than in groups.
3. Temperament. Some fish may be aggressive and attack others while some become prey. Choose fish that don’t fight or eat each other by instinct.
4. Temperature. If you are keeping tropical fish, they should be in 70-degree water and shouldn’t be mixed with cold-water fish.
5. Type of fish. There are generally two kinds of fish: tropical and cold-water ones. It’s better to put those with their kind.
6. pH levels. Tropical fish may require a specific pH level for their water, so you may want to do a little research on it.

Which fish can go well in a 20-gallon aquarium?

Don’ t know which fish to pick? Here’s a list of fish that you may be interested in keeping inside a 20-gallon aquarium:

1. Fancy Guppy – they have a very colorful tail and they are also livebearers. These fish can be active and can produce a lot so you may want to keep them in numbers that are divisible by 3 to avoid overpopulation.
2. Otoconclus – these shoaling fish are best in schools of 6 to 8 to avoid starving them and to avoid competition. They work best with algae wafers and they’re kind of like those janitor fish such that they stick to glass walls.
3. Molly Fish – the molly is a livebearer so they don’t lay eggs but still give birth in the same way as humans and mammals do. Two females and 1 male is an ideal ratio. The molly usually has a dark plum color.
4. Neon Tetra – bearing a luminescent color, the neon tetra is good for 20-gallon tanks as a small beginner fish, best in schools of 6 to 12.
5. Swordtail – having a pointy tail, this one is usually orange in color and should be kept with 1 male and 2 females in its ratio. They tend to have a slim shape.
6. Platy – the platy is usually good for beginners due to the size. A good ratio is 2 female fish and 1 male fish and you can increase that depending on your preferences. They tend to be active fish.
7. Dwarf Gourami – bearing a striking striped pattern, this species of fish can be a bit aggressive at times so it’s good to have just one male in the set of fish to avoid bullying or fights. Hiding spots can also be added to your fish tank.
8. Harlequin Rasbora – with a pattern that’s similar to Joker’s sidekick, this brilliant-looking fish is quite colorful to keep. They should be kept in schools of 6 or more. Don’t mix them with large fish!
9. Zebra Danio – made with stripes that look like a zebra’s stripes, this tropical fish is good for beginners and can be kept in schools of 6 or more. They need to have more space and playtime since they are active fish.
10. Cory Catfish – also known as the Corydoras, they can be kept in different varieties in a 20-gallon tank. They are great for eating leftover fish food since they usually go at the bottom of the tank. They eat mostly sinking pellets as well and are great tank cleaners.

Conclusion

In the long run, we think that the best filter for 20-gallon tank would be the Aquaneat Aquarium Bio Sponge Filter because it has a wide range of fish that you can use it for, as well as shrimps. It is both a mechanical and biological filtration method and it is easy to install as well.

While our other picks are fine, we picked this one since it was beginner-friendly for those who are just looking for a good filter to install in their basic fish tank.