How To Setup A 20-Gallon Fish Tank: Livestock and Equipment List

The fishkeeping world has come a long way, and today it offers a variety of choices. From a small pot to hundreds of gallons of tanks, you can get any. A medium-sized tank like a 20-gallon one is perfect for beginners for different reasons. Before adding fish to any tank, you must buy the parts and assemble them carefully. This assembling is a very crucial process for a fish tank and requires lots of patience and precision. Today we will be looking at how to setup a 20-gallon fish tank.

After reading this article, you will easily be able to choose the correct equipment for your 20-gallon tank. Also, I hope you will be confident enough to set up a tank on your own. A 20-gallon tank is quite large, so I recommend kids set up their tanks only under the supervision of any adults.

Why Is A 20-gallon Tank Ideal For Beginners?

Whether it is fishkeeping or any other activity, everyone should start easy and small. This reduces the chance of failure and demotivation. If your first shot is a success, even if it is small, you get motivated, pushing you to do more. This is simple human psychology, and everyone can relate to this.

We can apply this thing to fishkeeping too. A small tank, say, 10-gallon might look easy and petite, but it comes with a lot of challenges. A small tank is harder to maintain than a larger tank, and this is unarguably true. Only those people who can give more time to fishkeeping should keep 10-gallon tanks. This is a thing that every professional fishkeeper will suggest to you.

Protein buildup, algae overgrowth, cloudy water, and ammonia spike are major problems that you will face in a small tank all in a blink of an eye. Even leaving your tank unattended for 10-15 days can result in serious life-threatening issues. So, never start fishkeeping with a 10-gallon to 15-gallon tank.

A 20 to 50-gallon fish tank is ideal for beginners. Since anything larger than 20 gallons can be extremely large and expensive, a 20-gallon tank becomes the ideal choice for beginners. A 20-gallon tank can be classified as a medium-sized tank and is relatively easier to maintain than those small 10-gallon tanks.

How Large Is A 20-gallon Tank?

A 20-gallon is neither a small tank nor a big one. It might not fit in your study table but can add life to your living room.


You can setup a 20-gallon fish tank in two ways. One is tall, and the other being shallow. A shallow tank is better for fish that prefer being at the bottom or are bottom dwellers. A dimension of 30″ x 12″ x 12″ properly defines a long 20-gallon tank.

Some people prefer tall tanks, to save space and have tall plants. The dimension of a tall 20-gallon tank is 24″ x 12″ x 16″. These dimensions are important while choosing a proper stand or table for your tank.


An empty 20-gallon tank can weigh around 25lbs but might vary on the type of glass you are using. A full tank can weigh 225 lbs, including all the gravel and decors, but can vary according to the weight of the decors and gravels.

The same volume of saltwater and freshwater tank varies by almost 4 lbs, with saltwater being heavier.

A simple way to calculate the weight of your tank is by measuring the dimensions using a measuring tape. Take the length, breadth, and height (only up to water level) in inches and multiply them. Then multiply this volume by .004329 to convert it to gallons. Finally, by multiplying the number of gallons by 8.34 lbs/gallon, which is the density of water, you get the weight of your aquarium.

Note that this is just the water’s weight of your tank. Other factors like glass thickness, material, decors, and substrate also affect the weight.

Learn More: Aquarium Size and Weight Guide – A Shocking Truth

How Many Liters Can A 20-Gallon Fish Tank Hold?

Mathematically, 20-gallons is equal to 75.7082 liters. But since a 20-gallon tank doesn’t actually hold 20 gallons of water, the amount of water is less. It is fair to say that a 20-gallon tank has almost 18 gallons of water.

What kind Of Filter is Suitable For a 20-Gallon Fish Tank?

When it comes to a 20-gallon filter, you should choose something that is cheap, moderately powerful, provides enough circulation, and is easy to clean. In my opinion, hang-on back filters (HOB) are perfect for your 20-gallon tank. You can easily attach them to the aquarium glass, and they remain there tightly. Providing necessary mechanical and biochemical filtration, these HOB filters are worth all your money.

The minimum circulation rate that a twenty-gallon tank needs are 60-80 gallons per hour. Maintaining the minimum circulation rate prevents your tank from algae overgrowth, protein buildup, and dead spots.

Aqua Clear – Fish Tank Filter

This hang-on back filter comes for various tanks of sizes 20, 30, 50, 70, and 110 gallons. The AquaClear 50 model can be used in any tank ranging from 20 gallons to 50 gallons and is perfect for a medium tank. This filter is popular among fish keepers because the patented aqua clear refiltration system allows you to create a gentle flow for your fish without affecting the filtration.

Since this is a hang-on back filter, most of the part remains outside the tank, giving a lot of swimming space for your fish. The filter provides a beautiful waterfall effect to your aquarium. This filter uses foam insert, activated carbon, and bio-max ceramic rings to provide mechanical, chemical, and biological filtration. These media are placed at the bottom, middle, and top sections of the filter, respectively. At Amazon, its price is around $31, which is supposedly inexpensive.




The filter is simple to install, operate, and clean.

The filter needs manual filling or priming before starting.

It provides 3-stage filtration in the most efficient way possible.

This filter can get noisy at times.

It allows you to control the flow whenever necessary.

Since water gets exposed to the outside of your tank, there will be more evaporation.

If you use this filter, aeration won’t be an issue for your fish.

Which fish in a 20-gallon tank, and in what number?

Choosing the right fish for your 20-gallon tank is the most necessary part. All fish prefer specific tank sizes and conditions. A common rule widely followed by fishkeepers is to have one inch of fish for each gallon. So, a 20-gallon fish with 20 one-inch fishes is an ideal choice.

Guppy, Platy, Betta, Tetra fish

20-gallon is a perfect size for a small community of fish. This community must have nano fishes, with the total number not exceeding 25. I recommend fish like neon tetra, guppies, mollies, platies, and sometimes betta. Remember that when keeping betta, two males shouldn’t be kept together. This results in aggressive territorial behaviors and quarrels.

Bettas do good in a tank full of tetras rather than other fish. So, a community of 8-10 tetras and one betta fish is a great fish choice.

Another choice is livebearers like platies, guppies, and mollies. Five of each of these fish can establish a perfectly healthy community with no territorial brawls.

Best 20-gallon Starter Tank Kit

In the earlier days, there were no starter kits, and people had to buy every component separately. This was both time consuming and confusing. But today there are starter kits that come with a heater, filter, lights, fish food, gravels, additional water hoses, thermometer, and much more. Now we will be looking at the best 20-gallon starter kit, in my opinion.

Aqueon LED Aquarium Kit

Aqueon provides a complete starter kit that makes fishkeeping experience a lot easier. This 20-gallon starter kit is a powerful and spacious product that comes with everything your fish will ever need.

The most special thing about this kit is the powerful QuietFlow 10 LED PRO filter.  This hang-on back filter can easily provide 4-stage filtration, i.e., mechanical, biological, chemical, and wet/dry filtration. Dense floss, Activated carbon, Patented Bio-Holster, Diffuser grid, and Special filter pad work hand in hand to provide excellent filtration for your tank. The comes with a LED filter cartridge change indicator light that flashes when the cartridge becomes clogged with debris, reminding you to change or clean it. The filter is self-priming and starts working just after you plug it.

The kit comes with vibrant LED lighting to bring the aquarium to life. A 100W preset heater is enough to uniformly heat your tank. The LED hood is tightly secure and distributes light equally.

The kit has a dimension of 24 1/4″ L x 12 ½” W x 16 3/4″ H.



The filter has an indicator that reminds you of cartridge change. You have to remove the whole hood while cleaning or feeding the fish.
The LED hood lits the aquarium uniformly.
The kit comes with a fish-net, water conditioner, stick-on thermometer, and fish food.
The preset heater is durable and highly effective.

Best Stand For A 20-gallon Tank

Along with proper tank and fish, a strong stand is also important. A 20-gallon tank is quite heavy, and you need strong legs to support it. A perfect stand should be able to bear all the load that you land upon it.

Aqueon Forge Aquarium Stand

This stand is specially designed for the aquarium kit that I have mentioned above. The stand has durable steel construction and also has a rust-resistant powder-coated finish that makes it strong and sleek. The reversible wood panels allow you to change colors, brown or black. The stand also has an additional bottom shelf, which you can use for a second tank or anything else.

The setup process is easy and only takes 6-7, straightforward steps. You can easily assemble it by reading the user manual.




The stand has a strong build and can easily hold a 20-gallon tank. The setup might take long because of the stiff wood panels, and inaccurate pre-drilled holes.
Reversible wood panels allow you to choose between two colors.
The bottom shelf is also spacious and can occupy lots of stuff, even another tank.

Best Heater For A 20-gallon Tank

Since a 20-gallon tank is quite big, you must choose a heater that heats water uniformly all over the tank. Something with adjustable heat is quite popular nowadays, and it is everyone’s first choice. Now we will be looking at a heater, which I consider to be the best pick for a 20-gallon tank.

Aqueon Pro Heater Aquarium Heater 100 Watt

This is the same heater that coms free with the above-mentioned aquarium starter kit. Because it is built with a durable and non-corrosive shell, it is completely shatter-proof. The heater automatically shuts off when desirable heat is obtained. After the water has cooled dows, it gets back to work.

The manufacturers offer a limited warranty on the lifetime of this product. This clearly shows how durable it can be. The inbuilt LED turns red to indicate that the heater is still heating and turns green when it is not.

The adjustment knob offers a wide range of heat from 68-88 F. You can adjust among 68, 72, 76, 80, 84, and 88 F with Electronic Thermostat accurate to +/- 1 F. Sometimes achieving the right temperature can be hard because of the highly sensitive knob.




The heater comes with a limited lifetime warranty. The only problem is the sensitive temperature knob.
The shatter-proof design is trustworthy and ensuring.
Light indicators are also quite accurate and durable.


How To Set Up A 20 Gallon Freshwater Aquarium

When I started my fishkeeping journey, I didn’t have access to any starter kits. Today there are complete kits available at cheap prices (I have mentioned above) reducing your effort, time, and confusion. You get everything a tank needs, except for the stand. Whether it is an empty tank or a starter kit, here is how you can set up your 20-gallon tank:

The Pre-Setup

  • Finding a suitable spot for your tank is vital for your fish and other livestock. Place the tank where it won’t get direct sunlight and is safe, secured, and far from the reach of children and other pets like cats.
  • Then place your stand and a gyro-foam between the stand’s plate and the aquarium if necessary.
  • It is important to give the tank a thorough clean. So, using warm water and vinegar, you must clean the tank carefully to remove any dust particles or glue.

Adding Substrate, Equipment, Water, Plants, And Decors

  • After cleaning the tank, add the substrate. Before adding the substrate, you should rinse it properly. Finally, spread the substrate evenly using your hand.
  • Finally, you can add all your equipment inside the tank, like heater, filter, and lights, without switching them on.
  • Now add water to your tank. Place a vessel at the bottom of the tank and pour water carefully inside it. The vessel reduces the impact of water on the substrate and also prevents it from splattering all over.
  • Now, remove the vessel and add plants and decors. Remember to rinse plants properly as it can invite unwanted guests like ramshorn snails in your tank.
  • Finally, turn on the equipment.

Cycling the Tank And Adding fish

  • Although your tank now has everything that a fish needs, it is not completely ready to host life. The most important part, i.e., the nitrogen cycle, is yet to be performed. This process takes 6-7 weeks, and you can check our previous articles regarding how to cycle a tank.
  •  To add a new fish, float the water bag hat has the fish for around 20 minutes in your new tank to match both the temperatures. Hence, it helps the fish feel like home and adjust properly in the new ecosystem.

20 Gallon Fish Tank Setup Ideas

A 20-gallon tank can offer you a wide range of options than you think. Choosing the right option can be confusing but don’t worry, we are here to help. Here are the three most popular 20-gallons setup ideas.

Species-Only Tank

A species-only tank might sound boring, but trust me, it isn’t. A tank stocked with similar fishes with detailed colors can bring nothing but a joy to the eyes of a fishkeeper. In my opinion, tetra fish, guppies, bettas, tiger barbs, and kill-fish are best for a species-only tank. Especially keeping guppies like the blue delta tail guppies in a huge number of around 10-15 brings life to your tank.

A species-only tank allows you to focus on similar water parameters, and water-maintenance becomes a lot easier.

Community Tank

A community tank is always challenging and more beautiful than any other tank. In a 20-gallon tank, you can keep peaceful species like tetras, guppies, platies, mollies, and even bettas. But be sure to avoid bettas if you already have other long-finned fish like guppies. Here are two peaceful community tank ideas:

Secondary Tank for Breeding And Quarantine

You can breed fishes like bettas, guppies, and mollies in this tank. Since these fish don’t grow longer than 4 inches, you can start with a pair and build your community tank rather than buying all your fishes. People also use 20-gallons tanks as hospital tanks for bigger fish like cichlid. While medicating any fish, it is important to separate it from the main tank.

Maintaining A 20-gallon Tank

It is relatively easier to maintain a 20-gallon tank than a nano tank. Some basic rules for maintaining a 200gallon tank are:

  • Change 10% of the water every ten days. This helps to remove all the dissolved impurities like phosphates, nitrates, ammonia, etc.
  • Clean the filter media before it gets heavily clogged. One way to know about a dirty filter media is by looking at the water flow. IF the filter is producing less flow, it is time for a clean.
  • Remember to rinse the filter media only using the tank water. Using tap water might remove all of the good bacteria.
  • Also, perform a water test regularly to know about the concentration of dissolved impurities and pH. Then take necessary actions to improve the water conditions accordingly.
  • Check your electrical appliances regularly to avoid short circuits and electrocutions. Improperly sealed pumps, aerators, or other electrical devices can affect your fish heavily.

Tools/Equipment You Will Require to Setup a 20-Gallon Aquarium

Having some tools makes your fishkeeping experience a lot easier. These tools are not mandatory for all aquariums, but I recommend everyone to have them for a better fish keeping experience.

Air Pump

An air pump provides oxygen to your water by increasing the surface agitation. Air pumps are the backbone of air stones and air-driven filters but are not that important. Having them in the tank increases the concentration of oxygen and helps the fish a lot if there are a lot of members in the tank.


Sometimes the bubbles in a tank can be more attractive than the fish. A bubble also aerates the water properly and creates water movement. This can be a huge benefit ina 20-gallon tank with a large amount of livestock.


Debris like uneaten food and fish waste can stick tight between the gravels. Your filter won’t be able to pull it, and it will remain there forever, spiking the ammonia and causing other problems. The only possible way is to use a siphon to remove the water fro the bottom, including the debris. A siphon is a long pipe that can be truly beneficial during water changes.


It is almost impossible to catch fast-moving fishes like tetras and danios by hand. Putting your hand inside the tank is also not a good practice. Using a net every time to catch a wounded or pregnant fish reduces the stress on the fish. You can use a net to remove dead fishes and even decors for cleaning.

Watermaster Test Kit

Having a master test kit allows you to get an accurate chemical reading of your tank. A test kit usually measures pH, ammonia, and nitrate. These are the only factors that you must worry about in a freshwater tank. You can get accurate results within minutes and take necessary actions accordingly.


All in all, a 20-gallon tank is the best beginner tank and is easy to take care of. This tank provides you a variety of options, and all of them are excellent. If you want to start fish keeping, a 20-gallon tank can boost up your confidence and encourage you to do more. I think I have included everything related to setting up a 20-gallon tank, and I hope you will be able to do it on your own. The product link that I have provided above are trustworthy so, consider them while making any purchase.

Any feedback or recommendations are heartily welcomed in the comment section below.


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