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Best 20 Gallon Fish Tank for Fish

20 gallon fish tanks are ideal for beginners and anyone who’s on a budget. They’re more spacious than 10-gallon tanks and open you up to a wide variety of fish and plant species.

At this size, a 20-gallon tank isn’t so large that it racks up high maintenance costs, and it’s got just the right amount of water to maintain constant temperatures.

Here’s what you should know about setting up a 20-gallon fish tank.

But First: How Much Does a 20-Gallon Fish Tank Weigh?

Before bringing a 20-gallon tank into your home, you should know how much it will weigh.

For obvious reasons, an empty fish tank will weigh just a few pounds, but it will quickly go up to several hundred pounds when you fill it with water.

The first thing to start with is the dimensions of the fish tank. It’s measured by L (length), W (width), and H (height).

A standard 20-gallon tank will measure anywhere from 24 inches by 12 inches by 16 inches. It means that the total weight will increase up to 225 lbs.

For obvious reasons, it’s not going to be easy moving this mammoth of a tank around your house, and you should decide on the ideal location beforehand.

Another thing to keep in mind is the fish stand.

It is recommended to buy a specially designed 20-gallon tank fish stand instead of placing your aquarium over a makeshift dresser.

A dresser will buckle under the weight of a fully equipped fish tank, especially one that weighs well over 200 pounds.

Which 20 Gallon Fish Tank Should I Buy?

There are many sizes, shapes, and types of 20-gallon fish tanks out there. Some of these may come included with fish tank starter kits, while others will be empty, so you’ll have to buy your equipment.

We recommend buying your equipment anyways and not trust the quality supplied by your manufacturer (they usually cut corners to save costs).

Below is our pick of the best 20 gallon fish tank.

20 Gallon Fish Tank – Aquarium Kit by the Tetra Store

This tank is ideal for new fishkeepers who don’t have a clue about fishkeeping. It comes with a fully fleshed-out starter kit that includes a hood, integrated light, a filter, and a heater.

More importantly, it comes with four artificial plants that serve as an excellent tutorial before introducing live plants.

Setting up this 20-gallon fish tank is insanely straightforward. Add the substrate and your fish stock, and that’s all, folks!

There’s another reason why this tank made it to our list: the lifetime warranty.

The lifetime warranty means that your investment is safe and sound.

The dimensions for this aquarium are as follows: 24″ by 12″ by 16.”


  • Scratch-resistant glass
  • Lifetime warranty
  • The starter kit includes everything you could ever need
  • The filter is quiet and gets the job done
  • The hinged hood makes it easy to clean the tank


  • The plants look fake
  • The lights may be too inadequate for certain fish species

All in all, this aquarium is a sound investment. If you can’t find this model on Amazon, try searching on Etsy and Walmart.

Check out prices and availability on Amazon ( Click here to check )

20 Gallon Fish Tank Marina LED Aquarium Kit

The manufacturer went for a simple, minimalistic design. This Marina Aquarium features a standard rectangular shape, making it great for beginners in home and office environments.

Moreover, the tank easily blends into the office décor to stick out like a sore thumb. Its kit features stunning light fixtures that would make the fish feel right at home. A bonus feature of the light fixtures is that they can add more color to your room.

The LED light doesn’t disrupt the fish’s everyday life and is incredibly energy efficient, saving you energy bills in the long run.

This tank comes with the required filters that can install with the help of a simple clip-on filter. What we especially liked about the tank is the ability to swap out the filter cartridges with ease.

You can replace them with a few simple steps whenever maintenance is due. The filter aids in removing toxic pollutants and bioload, such as ammonia, leaving your tank with clean best water that will keep your fish happy for years to come.

Click here to check prices and availability on Amazon.

20 Gallon Fish Tank Half Moon Shaped Aquarium by Marineland (AML11536)

This aquarium features a stunning half-moon shape that will spruce up your interior décor. The kit comes with all the necessary equipment you could ever need, including LED light fixtures and a clear plastic canopy with small cutouts for feeding.

The canopy makes it easy (and quick) to feed your fish. Furthermore, the canopy minimizes water evaporation from the tank, reducing the need to refill the water to maintain its level continually. It’s super easy to install the filter in its position.

Note: The filter is not included with this model, but you can easily find one and mount one in the provided cutouts.

This review would be incomplete without mentioning the half-moon shape. Many fishkeepers will enjoy the view, which is only possible with this kind of design. The LED lighting and the unique view make for a stunning combination that is addicting to view.

The LED lights deserve special mention here. The kit comes with three blue LED lights and 42 white LED lights. You can control the color depending on the type of day. When installed in their correct positions, the LEDs create a shimmering effect that mimics the underwater effect of sunlight.

The nighttime LEDs mimic the fish’s biological clock, signaling that it’s time to sleep (or start hunting, depending on the species).

Click here to check prices and availability on Amazon.

Best Fish for a 20 Gallon Fish Tank

What fish are best for a 20-gallon fish tank? Below is our list of some fantastic fish for a 20-gallon tank. Of course, there are several more species that you can choose. The ones highlighted below are the ideal choice for beginners.

Adding Tank Mates in a 20 Gallon Fish Tank

Most fishkeepers want to build a thriving community aquarium, a tank where multiple species and ecosystems can live together with peace.

But there are a few things to keep in mind before adding tank mates, these include:

Water parameters: Only select tank mates that share the same water parameters, including temperature and hardness levels.

Aggression Levels: Adding aggressive species to a small 20-gallon tank is not advisable since they’ll give their tank mates a hard time. If you decide to add aggressive fish, make sure they’re the only specimen in the tank.

Schooling Fish: If you want your fish to live in a group, try to create schools of 6 or more. It will make them feel secure and happy in their new habitat.

Territories: Most fish species will carve out a small place in the tank and call it their home. Any fish that dare to swim closer will be given a hard time.

Make sure to give these territorial enough room in the tank. It will become too aggressive towards others in an overly populated tank.

Tank Columns: Not all species occupy the same column of the tank. Some species are top, bottom, and mid-water dwellers. Choose a combination of fish that occupy different column levels.

This way, they can be spread out over the aquarium instead of crowing into a single space.

Finding the Right Equipment for the 20 Gallon Fish Tank

Earlier in the blog, we asked you not to depend on the tank’s built-in equipment – they’re mostly low quality and will eventually give out. Therefore, it is best to invest in quality equipment that you can install in your tank.

You have to create a perfect, healthy environment for your fish. It includes the proper lighting to help them thrive and grow.

They need suitable substrate, temperature, plants, and decorations to hide and swim and stay healthy. More importantly, fish need purified water with a suitable pH and beneficial bacteria colonies to keep the tank clean.

Let’s get down to brass tacks.

20 Gallon Fish Tank Filter

A filter is an essential piece of equipment in a 20-gallon tank that you should never skimp out.

It provides your fish with clean and clear water. A low-quality, the cheap filter doesn’t do a great job and will fail much sooner than a higher quality product.

So investing in a good product from the get-go is a wise decision that saves you money in the long run.

As a general rule of thumb, your filter choice should easily filter through all of the water in the tank at least 3 to 4 times in an hour. A 20-gallon tank,

for example, will need a filter with a flow rate of 80 gallons per hour (or GPH). If you ask us, however,

it’s better to invest in a tank with a GPH that will filter the water 9 to 10 times an hour. More is better.

Types of filters you can see buying for your 20-gallon fish tank:

Internal filters: These filters are installed on the inside of the tank. It is easy to install internal filters, and maintenance is also reasonably straightforward. They are also very quiet (since they’re inside the tank).

Sponge filters: These filters are installed inside the tank. Their working mechanism is rather creative. They force water through the sponge’s large surface area with the help of an air pump or a powerhead. It allows them to act as a highly efficient filter (both bio and mechanical) that keeps the tank clean round the clock.

Hang-on-the-back: This typical tank hangs on the back of the tank. They’re not as bulky as canister filters and can’t sustain larger aquariums. More importantly, HOB filters are more budget-friendly and, therefore, ideal for your average aquarium enthusiast.

20 Gallon Fish Tank – Ideal Water Flow for Fish and Plant

Some fish prefer low to modest water movement like the Dwarf Gouramis. Others don’t like any water movement at all. Fish species like the Zebra Danios require high water currents round the clock.

Before adding water movement to your tank, ensure that all your fish stock will be comfortable with water currents.

Finding the Ideal 20 Gallon Fish Tank Heater

There are two things you should consider before choosing a heater for your 20-gallon tank: the ambient temperature of the room of the Heater’s quality.

Should select the capacity of the Heater based on the ambient temperature of the room. If your area has a warmer climate, your Heater should increase the temperature by 9° or less. In this case, choose a heater with a capacity of about 100 watts.

If the ambient temperature drops below 65° or more, then the Heater should have a capacity of about 200 watts to maintain a constant temperature.

When it comes to heaters, you get what you pay. They efficiently run into various maintenance issues, such as refusing to function after a few weeks of use, getting stuck, and even frying your fish! If you’re not careful, this may happen.

A cheap heater may seem cheap in the short run, but if you’re forced to buy a new one or have to replace all your fish stock in the tank, all of a sudden, that low price doesn’t seem like an advantage.

A high-quality heater should have the following features:

  • A temperature dial to make it easier to control the temperature
  • Safety shut off sensor to shut the Heater when the temperature gets out of control
  • Indicator light to help you know when the device is functioning

Submersible Heater best budget aquarium heater that will last you a long while. Choose from a range of options, including 50 watts, 100 watts, 150 watts, and even 300 watts.

Grave Vacuum

This piece of equipment is a lifesaver when it comes to tank maintenance. The gravel vacuum lets you remove water, fish waste, and other dirt out of the tank (and substrate).


You will have to clean algae that grow on the inside walls of your tank. For this purpose, you can buy generic sponges at your local grocery store. Just make sure they don’t come with any soap or chemicals.


It is vital if your source of water comes from the tap. Simply put, a de-chlorinator is a chemical additive that renders chlorine in your water harmless to your fish and bacteria.


Nets are proper if you need to add, catch, or move fish from one tank to another. It also comes in handy when you have to remove dead fish – that is a frequent occurrence in most tanks.


A lid can be necessary if your fish are jumpers and can escape. They also keep dust and bugs out and minimize the evaporation of water.

Test Kit

It is essential to test your water regularly, especially when you’re cycling your tank. It is of paramount importance to the water’s quality so you can improve it for the better. We recommend going with a liquid water test kit because they’re reliable and last longer than strips.

Setting Up a 20 Gallon Fish Tank

  1. Place the tank on level ground. Please make sure the entire base tank is supported; otherwise, it could develop leaks.
  2. Rinse the substrate and gently place it in the bottom of the tank. Create a nice 1″ layer of the substrate.
  3. Install your devices in the tank, including the filter, Heater, air pump, etc. Leave them unplugged for now.
  4. Add your décor, including rockwork, caves, and live plants.
  5. Fill the tank with water. Make sure to pour it slowly so as not to disrupt the substrate. Once you’ve added half the tank with water, time to add the live plants into the substrate.
  6. Use a de-chlorinator and start your devices.
  7. Place your lid and light fixtures in the tank.
  8. Cycle the 20-gallon tank, learn how to do it here.
  9. Add your fish to the 20-gallon fish tank.
  10. Stay on top of regular tank husbandry to keep everything running like clockwork.

Wrapping Up

A few key takeaways from this blog that we wanted to touch on:

Your tank needs regular maintenance. For example, when it comes to the water, it’s out with the old, in with the new. Your live plants will have to be pruned, the algae wiped clean off the tank, and you must remove the buildup of ammonia.

The more fish you add to the tank, the more you’ll have to maintain it.

And as always, research your fish species before you add them to your tank. You have an ethical responsibility to your fish –and they’re not just a source of entertainment.

We hope you enjoy this process. Setting up a new tank feels like a journey with infinite possibilities. You’re creating a literal work of art where your little fish buddies can hang out in peace.