Best 20-gallon fish tank

Fish & Reptile Supplies

A 20 gallon fish tank is large enough to provide your room with some lively ambience, but still small enough to be manageable for new aquarium owners.

BestReviews is reader-supported and may earn an affiliate commission. Details.

Which 20 gallon fish tank is the best?

A bubbling aquarium can provide hours of calming ambience and entertainment. While huge aquariums full of large fish and plants make a bold statement, those who are looking to house pet fish and keep their maintenance at a reasonable level should consider starting with a 20 gallon fish tank.

The Tetra Aquarium 20 Gallon Fish Tank Kit is an excellent value for those interested in adding an aquarium to their home. From the filter to the heater, this high quality glass tank includes everything you need to comfortably house a small collection of tropical fish.

What to know before you buy a 20 gallon fish tank

Fish species

The most important factor when it comes to deciding on an aquarium is making sure that it will be large enough to provide adequate living space for your fish. Many new to aquariums are surprised to learn that even small fish need a lot of room to live happily. A 20 gallon tank should only be expected to accommodate very small fish, frogs or shrimp. Be sure to keep in mind that many fish sold in stores are babies or juveniles that may quickly outgrow a 20 gallon fish tank.


It’s critical to select a location in your home where your 20 gallon fish tank can be permanently and safely set up. Avoid locations that receive prolonged, direct sunlight and be sure that your tank is within reach of the power outlets necessary to run its filter, heater and lights. Even these relatively small aquariums become very heavy once filled with water and tank decorations. Place your tank on a sturdy piece of furniture that is strong enough to bear the weight.


20 gallon fish tanks are available in both glass and acrylic. Generally, glass is the preferred material because it provides great visibility and resists scratching. Acrylic is lighter and less expensive to produce, but great care must be given to prevent the tank sides from accumulating unsightly scratches and abrasions from cleaning.

What to look for in a quality 20 gallon fish tank

Quality construction

Glass aquariums should be tightly built and sealed. They should have a plastic rim around the top to accommodate lighting fixtures and should not have excess glue smeared onto the viewing glass. Acrylic tanks are sometimes built as a single piece as opposed to panels. If you prefer an acrylic tank, select one that is crystal clear with no cloudiness or scratches from the manufacturing process


Starting a new aquarium requires you to invest in the equipment that you will need to keep your fish healthy. Filters, heaters, tank decorations, thermometers and more are just the tip of the iceberg. An aquarium kit that includes useful accessories will save you money, as well as prevent you from having to spend more time selecting each piece individually.


Traditional aquariums are rectangular. However, modern fish tanks are available in a variety of different shapes. Some are octagonal and others feature curved sides. The shape of the tank you select is largely up to your personal taste, although some consideration should be given to the species you intend to keep and how your tank will fit into your intended location.

How much you can expect to spend on a 20 gallon fish tank

You can purchase a 20 gallon fish tank for as little as $30 for the aquarium alone. Kits that include additional accessories cost $130-$150, and those that are available in unique shapes can cost $200 or more.

20 gallon fish tank tips

  • Provide shelter. Fish will often take refuge under plants or in small caves. To prevent your pets from becoming stressed, give them plenty of places to hide and explore.
  • Clean regularly. Aquariums require frequent water changes to prevent the buildup of harmful waste. For a 20 gallon tank, change 2 gallons of the water weekly. This will remove enough waste to clear the water, but also allow the aquarium to retain enough helpful bacterial cultures to keep your occupants healthy. Be sure the water you replace it with has been treated and is the same temperature as the tank you’re adding it to.
  • Research your pets. Not only do fish have unique requirements that vary by species, some also get along better in a community than others. Select fish that will not fight or display aggression to one another if kept in close quarters.

20 gallon fish tank FAQ

Will a 20 gallon tank be big enough for my fish?

A. Every species of fish will have unique requirements regarding the space and water conditions it needs to thrive. It’s important to thoroughly research your fish to ensure that it can be appropriately kept in a 20 gallon tank.

Can live aquarium plants survive in a 20 gallon fish tank?

A. Yes. Like fish, live plants need special consideration when it comes to their temperature and water quality. Be sure to select plants that are able to survive in the same conditions as your pet fish.

Can I keep a turtle in a 20 gallon fish tank?

A. Yes, depending on the turtle’s size. A 20 gallon fish tank can comfortably house a baby turtle or two, but these animals grow quickly and require a great deal of space. If you choose to keep a turtle in a 20 gallon fish tank, be sure to provide it with the UVB light and heat requirements that reptiles need to prevent death from diseases that occur under inadequate living conditions.

How do I treat the water for my aquarium?

A. Tap water contains chlorine and other chemicals that can harm or kill fish. To make sure that your aquarium is safe, select the appropriate water treatment solution from your favorite pet or fish store. Different fish species have different preferences when it comes to water acidity that you will need to familiarize yourself with. Test your water after treatment and allow your aquarium’s filter and heater to run for at least 24 hours before adding any plants or animals to your tank.

What’s the best 20 gallon fish tank to buy?

Top 20 gallon fish tank

Tetra Aquarium 20 Gallon Fish Tank Kit

Tetra Aquarium 20 Gallon Fish Tank Kit

What you need to know: A kit that includes useful equipment to help new aquarium owners get started quickly and easily.

What you’ll love: With its included lights, heater, filter, tank decoration and water treatment solution, this 20 gallon glass aquarium bundle saves time and money. This model is built in the USA.

What you should consider: Some users report that the accessories included in this tank kit are not high quality with some needing to be replaced after failure.

Where to buy: Sold by Amazon

Top 20 gallon fish tank for the money

Marina LED Aquarium Kit

Marina LED Aquarium Kit

What you need to know: A 20 gallon fish tank bundle that includes bright LED lighting on its lid and a useful starting guide.

What you’ll love: With a heater, filter, net and more, this aquarium kit is an excellent value for beginners.

What you should consider: Some users have replaced the filter that comes with this kit with one they purchased separately, citing that the included model is loud and hard to clean.

Where to buy: Sold by Amazon and Chewy

Worth checking out

SeaClear Acrylic Aquarium Combo Set

SeaClear Acrylic Aquarium Combo Set

What you need to know: An acrylic fish tank that’s a unique shape that is sure to be a conversation piece.

What you’ll love: This aquarium’s hexagonal design provides a unique viewing experience and opens up interesting placement and decoration options. Acrylic construction is light and crystal clear.

What you should consider: No accessories are included with this tank aside from a lighted hood.

Where to buy: Sold by Amazon and PetSmart


Sign up here to receive the BestReviews weekly newsletter for useful advice on new products and noteworthy deals.

Derek Walborn writes for BestReviews. BestReviews has helped millions of consumers simplify their purchasing decisions, saving them time and money.

Copyright 2021 BestReviews, a Nexstar company. All rights reserved.