The 20 gallon fish tank is one of the most popular fish tanks on our website. Not many people realize this but there are a few different 20 gallon fish tank shapes that are the same volume but each has it’s own orientation and use. This article describes all of the 20 gallon fish tank types and gives a review on the standard 20 gallon aquarium and each of its variants and brands available. The links in this post contain affiliate links and I will receive a small commission if you make a purchase after clicking on my link.
If you are in a rush here are our favorite 20 gallon aquariums and kits:
| Image | Title | Why We Like | Rating | |
|---|---|---|---|---|
 | 20 Gallon Long Aquarium | Best 20 Gallon Long (Aquarium Only) |  | Check Price |
 | Tetra Aquarium 20 Gallon Fish Tank Kit | Best 20 Gallon Fish Tank Kit | | Check Price |
 | GloFish Aquarium Kit | Best Neon 20 Gallon Fish Tank Kit | | Check Price |
20 Gallon Long Fish Tank
The 20 gallon long aquarium is typically sized at approximately 30″ wide x 12″ deep x 12″ tall. When people or stores refer to a 20 gallon aquarium they are usually referring to this size. There are a few standard brands that carry this 20 gallon long fish tank size including Oceanic, Aqueon, AGA, and Aqua Culture. The 20 gallon long is a great size because it gives you the great width of 30″. The shallow depth of 12″ allows for light to penetrate to the bottom of the tank if you are interested in planted freshwater tanks or growing coral in a full reef saltwater aquarium. Alternatively, these are a very popular size for small reptile enclosures as they allow a heat lamp to warm up a great basking area for your lizard or snake.
20 Gallon High Fish Tank
The 20 gallon high fish tank is approximately 24″ wide x 12″ deep x 16″ tall. It is 4″ more narrow than the 20 gallon long tank and 4″ taller. This size has become more popular over the last number of years because it takes up slightly less of a footprint than a standard 20 gallon long aquarium but still gives you 20 gallons of volume and allows for a very nice fish tank setup. Another advantage to this size is that a few popular aquarium manufacturers started offering full aquarium kits in this including Marineland, Tetra, Glofish, Aqueon, Marina, and Seaclear. Most kits contain everything needed to get started including a light fixture, filter, decoration, and air pump.
20 Gallon Extra High Fish Tank
This aquarium is twice as tall as the normal 20 gallon long fish tank coming in at 20″ wide x 10″ deep x 24″ tall. This tank is can really be described as two 10 gallon fish tanks stacked on top of each other because it comes in around the same dimensions. The 20 gallon extra high fish tank is a little harder to find compared to the other 20 gallon aquariums: they are very unique and really just are not as popular as the others so not a lot of the major manufacturers make them anymore. You will like this 20 gallon shape if are you looking for a uniquely “tall” aquarium for a reptile who likes to climb trees or for a fish tank or terrarium that you want to look deeper than wider. Currently we can find them from Deep Blue and Aquarium Masters.
Tetra Aquarium 20 Gallon Fish Tank Kit
Tetra Aquarium 20 Gallon Fish Tank Kit is an all-inclusive option that has excellent reviews. The package includes all of the equipment required for setting up an aquarium. Its 20-gallon tank measures 24.2” (L) x 12.4” (W) x 16.7” (H) and is made from scratch-resistant glass. It has adequate space and will be suitable for many fish species. A hood with integrated LEDs for lighting, a Tetra Whisper 20 Filter, and one Tetra Mini UL Heater are other items provided in the package. The decorations in the box include one Boxwood plant mat and four artificial plants. You only require gravel and fish to set up your aquarium. Overall, it is a great product with superb 20-gallon fish tank reviews.
Tetra ColorFusion Aquarium 20 Gallon Fish Tank Kit
The ColorFusion Aquarium 20 Gallon Fish Tank Kit is an alternative option from Tetra that is backed by favorable fish tank reviews. It uses the same tank, measuring 24.2” (L) x 12.4” (W) x 16.7” (H), but switches the internal décor to change the aesthetic appearance of the aquarium. The hood has integrated Color Fusion Universal Color Changing LED lighting. You can cycle through the colors or select a single one for altering the aquarium’s internal appearance, a feature that earns this 20-gallon fish tank great reviews. Tetra ColorFusion Aquarium 20 Gallon Fish Tank Kit also includes one Tetra Whisper 20 Filter, one UL Heater, and one blooming white anemone and two wonderland plant multipacks. You can begin fishkeeping in no time with this package.
GloFish Aquarium Kit Fish Tank with LED Lighting and Filtration Included, 20-Gallon
If you are searching for commendatory 20-gallon fish tank reviews, then the GloFish Aquarium Kit fish tank is another suitable option. The aquarium has dimensions of 27.88” (L) x 16.13” (W) x 20.38” (H). Its hood has integrated lighting and features a GloFish 13” LED light stick. It is suitable for fluorescent fish species that glow in neon colors. A Tetra Whisper 20 filter is provided along with a Tetra mini UL heater for facilitating an appropriate living environment for your aquatic pets. Decorations bundled in the package include one GloFish yellow anemone and a pair of plant multipacks. You only need to purchase fishes and gravel separately. The GloFish Aquarium Kit fish tank has superb reviews due to its colorful, neon display. It will appeal to most buyers.
Aqua Culture 20-Gallon Aquarium Starter Kit With LED
Another bundle with positive 20-gallon fish tank reviews is the Aqua Culture 20-Gallon Aquarium Starter Kit. The tank measures 25.75” (L) x 14.25” (W) x 18.62” (H) and will suit quite a few homes and establishments. It has a low-profile hood that features a cutout for easy switching of the filter cartridge. There is a Tetra internal filtration system provided in the bundle. Integrated LED lighting illuminates the aquarium while giving the water a shimmering appearance. No decorative items are provided in the package, and you will have to purchase them separately along with gravel and fish.
SeaClear Acrylic 20-Gallon Deluxe Hexagonal Aquarium Combo Set
Buyers who are searching for unorthodox 20-gallon fish tanks with rave reviews can consider the SeaClear Acrylic 20-Gallon Deluxe Hexagonal aquarium combo set. Its tank has a hexagonal shape instead of being rectangular. It requires less space as it is taller than wider with dimensions of 15” (L) x 15” (W) x 24” (H). The tank is made of acrylic and is clearer and lighter as compared to glass aquariums. A reflector and a 12” lighting fixture are provided along with the tank. There are three color options that buyers can choose from – black, clear, and cobalt blue.
20 Gallon Fish Tank Guidelines
20 gallon fish tanks are many people’s first, second, or “forever” fish tank because they are still a manageable size but they give you that much more room than a standard 10 gallon fish tank. Here are a few specs or guidelines on a standard, 20 gallon long fish tank if you are considering purchasing one:
Number of Fish
If you follow the typical rule of thumb that you can hold 1″ of fish for every gallon of water than if you have fish at an average of 2″ to 3″ you will be able to hold about 7 fish in your new 20 gallon aquarium if it is freshwater. It will be less than that for saltwater. Please note that it is recommended you start at 25% of that capacity to begin and please test the water after 6 weeks to ensure that your aquarium is maintaining proper filtration to minimize nitrate or ammonia spikes. Most people are tempted to reach the “maximum” amount of fish that you can place in an aquarium but please keep in mind that the more fish you have in a single tank the more you will have to keep up with the maintenance of that aquarium without risking reduced water quality for your fish.
Heater Size
A 20 gallon aquarium requires approximately 100 watts of heat so you would need either two 50 watt heaters or one 100 watt heater. Luckily 50 watt or 100 watt heaters are a common size for purchase so these should be easily located in your local fish store. Although slightly more expensive, we recommend purchasing a titanium aquarium heater to avoid some common troubleshooting occurrences with glass heaters such broken glass or errant voltage within you aquarium.
Filtration
A freshwater 20 gallon fish tank should have a filter that pushes at least 100 GPH of water through the filter. For saltwater roof tanks the flow should be between 100-200 GPH of total water flow (between the return filter pump and powerheads or similar). At the 20 gallon size there are a many different types of water filters available to you depending on that you would like to put into your aquarium such as a canister filter, corner air filter, biowheel filter, or a full sump and/or refugium with a skimmer inside of it (popular for saltwater aquariums.)
Lighting
A 20 gallon fish tank should have at least 10 watts of light (for a non-planted freshwater tank) up to 100 watts of light for a full saltwater reef tank. Please note this is for standard florescent bulbs, LED lights would require much less! A 20 gallon fish tank can accept many different types of light fixture but I would use caution if you plan to use a metal halide fixture as those have a tendency to heat up pretty hot and a 20 gallon fish tank wouldn’t take very much to heat up the water.
As mentioned above the 20 gallon fish tank is one of the most popular in the aquarium hobby. If you are looking to purchase one I would recommend following the advice above. If you would like to build your own 20 gallon “package” with the guidelines above or purchasing a full 20 gallon fish tank kit as described above.
What are the Best 20 Gallon Fish Tanks?
We are always on the lookout for new designs and manufacturers of fish tanks. The 20 gallon fish tank is a classic size and has been made for decades, but some manufacturers are giving the classic 20 gallon fish tank some of their own uniqe twists. Here are a few of our favorite 20 gallon fish tanks available today.
