20 Gallon Fish Tank Setup

20 Gallon Fish Tank Setup Guide

The 20-gallon aquarium or fish tank is ideal for beginners. It’s big enough to house a variety of fish but small enough to keep.

This size tank allows you to have a variety of fish as well as live plants, and other inhabitants like snails or shrimps.

How do you begin? With the hundreds of tanks, fish and equipment that are available, it’s hard to know where you should start.

This article will discuss the top 20 gallon tanks and how to install them. We’ll also give you some stocking ideas.

What You Need to Know About 20 Gallon Fish Tanks

While most beginners start out with 10 gallon tanks, it is better to get a 20 gallon Aquarium.

The tanks are usually sold in a kit. This makes it easy for beginners, as they do not need to worry about the other clownfish pokes its head out of a sea anemone equipment needed.

The majority of people do not realize that the bigger the tank is, the easier it will be to maintain the water level ( this is a problem faced by most beginners).

These tanks are not only great for beginners, but they also work well as quarantines to separate new fish. They can also be used to separate fish from the main tank.

The 20 gallon tank is also perfect for experienced aquarists. They can be used in to set up small biotope aquariums or as breeding tanks because of their perfect size.

The dimensions of most 20 gallon tanks are larger in length and width than in height. The dimensions of a 20 gallon aquarium are typically 24″L x 12″W x 16″.

Tanks are available in two shapes: the rectangular or cube-shaped tanks shown above, and also in glass or acrylic.

Best 20 Gallon Aquarium Tank

Best Starter Kit: Tetra 20 Gallon Aquarium Kit

Best 20 Gallon Aquarium Starter Kit

This is the perfect aquarium for those who want a starter kit.

This complete aquarium kit comes with a 20-gallon aquarium, as well as a hood that has an integrated LED light, a heating element, and a filter.

The kit also comes with four artificial plants that are perfect for beginners who want to get a taste of keeping fish and live plants before diving into the world.

It doesn’t get any easier. Just add the gravel, and then the fish.

The kit comes with a lifetime guarantee and other essential pieces of equipment, such as a tetramine, aquasafe and fishnet.

Aquarium Dimensions: 24.2-inches x 12.4-inches x 16.7-inches.

  • Easy maintenance with the hinged hood.
  • Scratch-resistant.
  • This package includes everything you need to start.
  • Lifetime Warranty
  • Quiet filter.
  • Thermometers on the outside of the tank.
  • The plants are clearly artificial.
  • Hood is a little flimsy.
  • The lights don’t seem to be very bright.

Best Aquarium: SeaClear Acrylic Aquarium

Best 20 Gallon Aquarium Tank

This is a great alternative to glass aquariums. It’s stronger and lighter.

The tank comes in many different sizes and forms. The 20-gallon version comes in both a rectangular and hexagonal shape.

Acrylic aquariums are half the weight of glass tanks and much stronger. It is therefore less likely to chip or crack, making it ideal for families who have young children.

SeaClear, one of the best-known companies in the aquarium business, is the manufacturer behind this tank. You can therefore expect it to be top quality.

This aquarium includes a 15″ light fixture and a reflector. It is perfect for people who prefer to select their own equipment.

Aquarium Dimensions: 23” by 13” by 16”.

  • Aquariums made of glass are lighter and stronger.
  • SeaClear is one of the most respected companies in the aquarium business.
  • Glass tanks are not as clear and do not provide a good view.
  • Safety is a major benefit of rounded corners.
  • The openings in the main are not very large, so it can be difficult for fish to be fed.
  • Plastic hood is flimsy.
  • The enclosed top is difficult to maintain and clean.

Most Affordable Aquarium: 20 Gallon Glass Aquarium

Most Affordable 20 Gallon Aquarium Colorful Fish On A Reef Aquarium

Use this tank as the base for your own custom setup. It is a sturdy and high-quality tank.

You can create your own aquarium setup using this simple 20-gallon aquarium. You can choose the quality of equipment you want to use.

If you want to keep it simple, you can opt for the quarantine tank setup.

This is a quality tank made of glass with a triple-strength bottom. All sides are sealed with silicone rubber to ensure that they last for many years.

Aquarium Dimensions: 12” by 16” by 24”.

  • Tanks that are solid and durable.
  • You can add your own equipment.
  • The tank is of excellent quality and at a great price.
  • You can use it for many things, including keeping reptiles and fish.
  • Silicone isn’t uniform.
  • It’s important to find the right hood.
  • Some models are made of black silicone and others with clear silicone.

Cube Aquarium Coralife LED Biocube

Cube Aquarium

This kit is a unique starter kit of high quality for either a freshwater or saltwater tank.

This tank is a little different than the others we’ve shown.

The aquarium comes with a vibrant LED lighting system that can be adjusted to three different settings: bright white, sparkling bluish or color enhancing.

These lights have a timer that runs 24 hours and is set to replicate the natural cycle of day. There are settings for sunrise and sunset, as well as moonrise and setting.

The filtration system is also built in. It’s a new Biocube style, and the company has added 2 inches in height to make their new aquariums bigger.

Dimensions of the Aquarium: 15″ x 16.8″ x 17.5″

  • Excellent lighting system
  • New model offers more space.
  • Filter built into the device.
  • Acrylic is used to make this product.
  • Back compartment has space for UV sterilizer and skimmer.
  • Aquariums with a rectangular shape have a wider width.
  • The fan in the lid is noisy.
  • The small compartment in the back makes it difficult to change sponges.
  • Plants that need more intense light can benefit from the use of these lights.

Best 20 Gallon Aquarium Tank Equipment

Best 20 Gallon Aquarium Tank Filter

Filters are required for almost every fish tank . There are many reasons why filters are necessary.

They remove debris from the water. Second, they aerate water to allow for your fish to breathe.

Thirdly, they remove any toxic buildup that has built up.

You will need to perform regular maintenance on your filter and replace the media according to the instructions of the manufacturer. This should be done at least every two months.

Best 20 Gallon Aquarium Tank Heater

You may need a heater depending on the fish that you plan to keep.

The speaker said that a tropical tank is more likely to have a wider variety of fish, as long as you use a heater to heat the water.

Best 20 Gallon Aquarium Tank Lights

Aquarium Lights serve a variety of purposes. These lights can be used to illuminate the aquarium and show off the colors of the fish.

The main reason for having lights in your aquarium is to help your fish and plants. It helps them regulate themselves and maintain their environment as close as possible to what they would experience in nature.

You will need different lights depending on what kind of plants and fish you intend to keep. Some plants need more light than other types.

Best 20 Gallon Aquarium Tank Hood

Hood with LED lights

This hood is equipped with both daytime and nighttime LED lights. It can be used for any 20 gallon system.

The hood will be included in most kits, but you may need to purchase one separately if you are buying a tank.

For most setups, a hood is required to keep out jumping fish such as killifish and to stop anything from falling into the tank.

You should also wear a hood to prevent excessive water evaporation.

Other Equipment

You will also need:

  • Gravel
  • Dechlorinator
  • Decorations (Including live or artificial plants)
  • A fishing net
  • A gravel siphon
  • An algae magnet

What Fish Can I Keep in a Twenty Gallon Tank

When it comes to buying fish for your aquarium, research is key.

It is important to make sure that the fish that you plan to add will be compatible with one another. They should also not grow too large for the tank, and they must all be able to live in the same conditions of water (pH and temperatures).

There are so many options for what you can put in a 20-gallon aquarium. This size tank can hold almost any small fish.

You’ll find a list with the top fish for this tank. We will also give you some information about their sizes and preferences.

  • Guppies- can grow to 2.5″ in length. Most people keep male guppies because of their vivid colors.
  • Platies are active, fun and can grow to 2.5″ in length. Two females should be kept for every male.
  • Swordtails- can grow to a maximum of 4”. They are peaceful and require a lot of space for swimming.
  • Mollies are available in many colors and can grow to up to 3″ in length. They have a peaceful temperament.
  • Neon Tetras only reach a maximum of 1.25”. They have a beautiful coloration, and should be kept with a minimum of 6 students.
  • Harlequin Rasbora- these fish can grow up to 2″ in length and prefer to be kept with a school of 8 or more.
  • Zebra Danio These beautiful striped fish can grow up to 3″ and should be kept with 6 other fish.
  • Cory Catfish This gentle, bottom-dwelling fish can reach a maximum size of around 2.5″
  • Dwarf Gouramis- These beautiful 2″ fish will add color to your aquarium.

20 Gallon Tank Ideas

It was mentioned earlier that it’s important to pair fish so you can create an ideal environment.

We’ve listed for your convenience four ideas of setups that work well with a 20 gallon aquarium.

Option One: A Species Tank

One of the most impressive tanks that you can have is a tank with only one species.

You can then focus on what you need to do in order to bring out the best of their colors and behaviors.

Examples of species-only tanks include Neon Tetras, Killifish, and a Betta Sorority Tank.

Option Two: A Breeding Tank

You can use an aquarium to create a breeding tank as long as your species doesn’t get much larger than 3-4″

Guppies, Swordtails , and Platies are all examples of livebearers that breed easily.

Option Three: A peaceful community tank

You can create a community of peaceful small fish in your aquarium if you want to add more variety.

You shouldn’t encounter any problems as long as you keep all your fish in the same environment.

Some people create biotope tanks, which are water tanks that replicate a specific area or body.

Examples of community tanks include:

  • Three Guppies and two Mollies.
  • Five Neon Tetras and five Glowlight Tetras. Three Black Phantom Tetras.

Add some snails or shrimps to the community setup.

Option Four: Coldwater Tank

There aren’t many options available if you wish to create a cold-water aquarium.

There are many fancy varieties of goldfish, which is one of the most common cold-water fish. Most of them, however, require at least 20 gallons of water per fish. This means you can only have one goldfish.

How to set up a 20 Gal fish tank

First, clean your tank thoroughly. You can use a soft cloth to remove any dust, if the tank is new, or white vinegar and warm water, if you have used it.

After your tank has been cleaned, you will need to choose the exact location where it will be installed. Select a flat surface away from radiators and windows.

Put all of your equipment into your tank and add the gravel.

Pour water into your tank and place a bowl over the gravel. The bowl will help reduce the impact the water has on the gravel.

Add the plants and decorations once your tank is filled. At this point, you can also switch on your equipment.

Add a bacteria starter to the water (optional). Many people think that adding a bacteria starter will allow you to add fish within a few days. This is not the case.

You need to cycle the tank. It is important to let a healthy bacteria bed develop (this will reduce toxic compounds like ammonia and nitrogen oxides).

The process could take up to six weeks.

Add your fish by floating the bag for 15 to 20 minutes in water, then adding a cupful every 10 minutes.

You can then add your fish to the tank once the bag has been filled and the fish have adjusted to the water temperature.

What Is the Best 20 Gallon Fish Tank?

Your budget, what you want and its purpose will determine the type of tank you buy.

If you are looking for a complete kit that is relatively inexpensive and you don’t need to think about it too much, the Tetra may be the best choice for you.

If you don’t have a budget and are willing to spend more money, SeaClear, or Coralife Aquarium, will be the better option.

If you are looking for something bigger, read our guide on 30 gallon aquariums.

See below our guide to some of our recommendations for a good 20 gallon tank. 

Aqueon Aquarium Fish Tank Starter Kit with LED Lighting

20 Gallon High Fish Tank with Aqueon Flexible LED Bubble Wand Blue 21 Inches Bundle

  • Product details

    • Date First Available ‏ : ‎ November 25, 2021
    • Manufacturer ‏ : ‎ Aqueon
    • ASIN ‏ : ‎ B09MK9LP1L

Our Tanks

Aqueon, developed by aquatic enthusiasts, offers a wide range of aquarium products to maintain healthy aquatic environments. Aqueon’s goal was to do what is best for fish health and the well-being aquatic life. The little details will simplify your aquarium-keeping and keep you and your fish happy and healthy. Aqueon is all about fish.

    • The box contains all the necessary equipment to start.
    • Includes: Glass aquarium, Low Profile LED Hood, QuietFlow Power Filter, Filter Cartridge, Submersible Preset Heater, Premium Fish Food Sample, Water Conditioner Sample, Fish Net, Thermometer and Setup Guide
    • Each week, add one PURE to every 10 gallons.
    • When starting a brand new aquarium, add two PURE tablets per 10 gallons.
    • Magnets make it simple to clean aquariums inside and out
    • The weighted scrubber won’t float!

Tetra ColorFusion Aquarium 20 Gallon Fish Tank Kit

Includes LED Lighting and Decor

Target Speciesfish
Special FeatureLightweight
Item Dimensions LxWxH27.88 x 16.13 x 20.38 inches
ColorColor Fusion
Included ComponentsSee package
Product Dimensions24.2″L x 12.4″W x 16.7″H

About The Tank

The LED lights will transform your aquarium as they change colors. You can pause the color cycle at any time to customize your aquarium.

Anemones move with the filter current, giving your fish somewhere to relax and hide.

Color Fusion LEDs bring Tetra Plants to life

Tetra ColorFusion Kit Includes: One 20 Gallon Glass Aquarium, One Aqua Hood, Tetra Whisper 20, one Color Fusion Universal Color Changing Led, Two Wonderland Plant Multipacks and one Blooming White Anemon

Aquarium Dimensions:24.2 L x 12 W x 16 7 H

Product details

  • Product Dimensions ‏ : ‎ 27.88 x 16.13 x 20.38 inches; 34.45 Pounds
  • Item model number ‏ : ‎ NV33822
  • Date First Available ‏ : ‎ August 17, 2015
  • Manufacturer ‏ : ‎ United Pet Group
  • ASIN ‏ : ‎ B013BXDXTC
  • Country of Origin ‏ : ‎ USA

GloFish 20 Gallon Aquarium Kit with LED Lights

Decor Heater and Filter

Target Speciesfish
Tank Volume20 Gallons
Special FeatureLightweight
Item Dimensions LxWxH27.88 x 16.13 x 20.38 inches
Item Weight15.6 Kilograms
StyleTank Kit

About this item

  • The blue LED light completely transforms your aquarium
  • GloFish and fluorescent décor create a colorful, neon display
  • GloFish Glass Aquariums are made in the USA and are built to last with scratch resistant glass
  • The Tetra GloFish Kit includes: one 20 Gallon Glass Aquarium, one LED hood, one Tetra Mini UL Heater, one Tetra Whisper 20 Filter, one GloFish 13″ LED Light Stick, three GloFish Plants, one GloFish Yellow Anemone. Add gravel and fish to complete your aquarium.
  • Aquarium Dimensions: 24. 2″ L x 12. 4″ W x 16. 7″ H
  • Age range description: All Life Stages

Product details

  • Is Discontinued By Manufacturer ‏ : ‎ No
  • Product Dimensions ‏ : ‎ 27.88 x 16.13 x 20.38 inches; 34.39 Pounds
  • Item model number ‏ : ‎ NV33823
  • Date First Available ‏ : ‎ August 17, 2015
  • Manufacturer ‏ : ‎ United Pet Group
  • ASIN ‏ : ‎ B013BXE1XO
  • Country of Origin ‏ : ‎ USA

How to care for GloFish®


Fish can be fed in small amounts up to 3 times per day.

Keep the water between 72 and 80 degrees. It is wise to use an aquarium heater, particularly during the winter.


GloFish Color Booster is a great way to keep GloFish (R) in a healthy environment and enhance their colors.

Tetra Water Care App allows you to track your results and test water with Tetra EasyStrips (T-M).


Rinse your gravel and décor with water before setting up. Do not use any soaps or chemicals.

Choose a place that is flat, away from sunlight or air conditioner vents.

Create a slope upwards by adding gravel.

Tetra Aquarium 20 Gallon Fish Tank Kit

Includes LED Lighting and Decor

Target Speciesfish
Tank Volume20 Gallons
Special FeatureLightweight
Item Dimensions LxWxH27.88 x 16.13 x 20.38 inches
Specific Uses For ProductIndoor

About The Tank

Tetra Glass Aquariums, made in USA with scratch-resistant glass, are durable and built to last.
Tetra Aquariums come with a LED Hood that creates a daytime look and feel, as well as a Whisper Filter, which is quiet, but provides powerful water flow.
Artificial Plants give your aquarium a natural, unique ocean feeling while providing a hiding place for fish to reduce stress.
This kit includes a 20 gallon glass aquarium, a Tetra Mini UL heater, a Tetra Whisper 20, simulated Boxwood Plant Mat and four synthetic plants. Complete your aquarium with gravel and fish
Dimensions of Aquarium: 24.2″L x 12″W x 16.7 H

One of our favourites:

Aqueon Saltwater Fish Small Starter Kit Bundle

Target SpeciesFish
Special FeatureLightweight
StyleSmall Saltwater Bundle

About The Tank

  • Coralife LED BioCube Aquarium Fish Tank Kit, 16 Gallon
  • Coralife BioCube Aquarium Cleaning Magnet, Small
  • Aqueon Aquarium Fish Tank Water Conditioner Bottle, 16 oz
  • Aqueon Preset Aquarium Fish Tank Heater, 100 Watts
  • Coralife BioCube Marine Salt, 15G

Everything you need is included in the compact, customizable filter chamber built into the rear of the aquarium. Easy to set up and maintain.

GREAT FEATURES: Includes a quiet submersible Pump, dual intakes, and an adjustable return nozzle.Compatible with existing BioCube Accessories.Separately sold are fish, corals and substrate.

Sleek and Modern – Biocubes features a round edge design, and it is an innovative and all-inclusive all aquarium that will suit all your needs.

The low-profile hood is equipped with vibrant LED lights that are capable of growing and maintaining healthy corals.

MAXIMIZE BETTER – A 24-hour timer that makes it simple to adjust the brightness of three separate light channels: sparkling blue, bright white and LEDs with color enhancement.

The SUNRISE/SUNSET mode is an automatic function that simulates a day/night cycle in your aquarium. It includes a 30-minute sun-rise/sun-set timer and combines it with 59-minutes of moonrise/moonset.

Coralife, a brand you can trust for marine aquarium supplies and parts.Our products include aquarium lighting, salt mixes, and filtration systems.Coralife is there to help when aquarium systems need more than the basic.

Coralife BioCube Curved glass aquarium cleaning magnet, small

  • Falls straight down
  • The float will not go away
  • The rake rests on the gravel to make retrieval easier
  • The ideal aquarium for tanks up to 29 Gallons or a thickness of 1/4″.
  • The curved aquarium for glass is designed to fit the curved shape of your aquarium.
  • The sled falls straight down, resting on the gravel to make it easy to retrieve
  • Weighted scrubber
  • Magnet for cleaning algae

One of Coralife BioCube marine fish tank aquarium salt, 15 gallon

  • It neutralizes chloramine and chlorine, as well as reducing the phosphate content to limit algal growth
  • The formula can be used for RO or tap water
  • The fine grind is for rapid dissolution
  • Easy mixing with the included scoop which precisely measures 1 gallon salt mix

1 of Aqueon Aquarium Fish Tank Water Conditioner Bottle, 16 ounces

  • When adding water to aquariums, filling them with tap water or performing water changes.
  • Makes tap water fish-safe instantly
  • Supplement to fish stressed by transport, netting or stress
  • The fish waste is detoxified of heavy metals and ammonia.
  • Included is a convenient dosage cap

1 of Aqueon Aquarium Preset Heater for up to 40 Gallons, 100 Watts

  • Set to 78 degrees, accuracy to 1 degree.
  • No adjustments required
  • Shatter Resistant
  • Auto shut off when it overheats. Resets itself when it cools.
  • When aquarium water is heated, LED lights will turn on.
  • Perfect for aquariums of up to 30 Gallons

Marina Aquarium Kit - 20 gallon Fish Tank - LED

Target SpeciesFish
Special FeatureLightweight
Item Dimensions LxWxH24 x 12.5 x 16.5 inches
Specific Uses For ProductIndoor
Style20 gallon
Included ComponentsLED Aquarium Kit

About The Tank

  • 20 U.S. gallon glass aquarium
  • Includes a Marina Slim S20 clip on filter with quick change filter cartridges
  • Includes everything you need to get your aquatic home started
  • Measures: 24 inches L x 12.5 inches W x 16.5 inches H

Marina LED Aquariums

The Marina LED Aquarium Kits are ideal for beginners. They come with all the necessary equipment to help make their first experience in the world of aquarium fish keeping a fun and easy one.

Included & Features

  • Marina Slim S10 and S20 Clip-on filters with Quick-change cartridges
  • The aquarium canopy is fitted with a long-lasting LED module that produces a natural daylight effect.
  • Keep fish healthy with Fluval Max.
  • Fluval Aqua plus Water Conditioner makes tap water fish-safe
  • Fluval Cycle Biotic Supplement creates a biologically balanced environment.
  • Protect delicate fins with a fish net made of fine, soft mesh.
  • Aquarium care guide with advice for setting up and maintaining your aquarium

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