Best 20 Gallon Fish Tanks (2026): Kits, Bare Tanks and Rimless

Tetra's listing for its 20 gallon kit includes a glass aquarium with a low-profile hinged hood, an LED lighting system, an internal filter and cartridge, an aquarium heater and thermometer, and a water conditioner sample. The tank measures 24 by 12 by 16 inches, the 20 high shape.

The filter uses mechanical floss and Tetra's carbon. Rinse the cartridge in tank water rather than replacing it monthly, or add a bag of ceramic media to the filter, so the bacteria that keep fish alive are not thrown out with each cartridge. Our filter media guide explains why.

Tetra's own page for this kit (item NV84004) is more specific than the listing. It names the filter as the Whisper PF 20 power filter with a Large Bio-Bag cartridge, sizes the heater at 100 watts, and adds a net and a TetraMin food sample. That heater suits the tank: Tetra rates its own 100 W HT30 preset heater for 10 to 30 gallons. The listing still calls the filter internal, so check which one arrives before buying spare cartridges.

Aqueon sells its SmartClean starter kit in a 20 gallon size. Its contents bullet appears to be copied from the 10 gallon kit: it lists a "10-gallon" aquarium and a 50 W preset heater, while the listing's size is 20 gallons. We flag this because a 50 W heater is undersized for 20 gallons by EHEIM's table, which rates 75 W for about 60 to 100 liters (16 to 26 gallons). Check the box; if it does include a 50 W heater, add or swap for a 75 to 100 W one in a cool room.

Otherwise it is a sound kit: LED hood with a feeding door, the SmartClean filter, a preset heater, a thermometer, a net and food.

Two more clues point to the shape and the heater. The listing's dimensions line gives 24.25 by 12.5 by 16.75 inches, which is the 20 high on Aqueon's chart, not the 20 long. And Aqueon's own kit page lists one set of contents for both its 10 and 20 gallon sizes, including a 50 W preset heater, so plan on a larger heater if your room runs cool.

The GloFish 20 gallon kit lists a 24.2 by 12.4 by 16.7 inch glass aquarium, an LED hood, a Tetra Mini UL heater, a Tetra Whisper 20 filter, a 13 inch GloFish LED light stick, three plants and an anemone. The listing says the glass is made in the USA and scratch resistant.

It is a complete, kid-friendly setup with a strong theme. Add gravel and a thermometer, cycle it, then add fish.

Aqueon's bare 20 gallon high is 24.25 by 12.5 by 16.75 inches and weighs 26.6 pounds empty, per its listing, with a five-year limited warranty. The listing also recommends a properly rated stand for a fully filled tank and drip loops on electrical cords, which is good advice for every tank.

Build around it with a Fluval AC30, a 75 to 100 W heater and a light sized for 24 inches. Aqueon also sells the 20 long and 29 gallon in the same line.

Lifegard's Crystal rimless 20 gallon uses ultra-low iron glass, 5 mm thick, with 45-degree beveled edges bonded with clear silicone and an insulation pad, according to its listing, which gives a one-year warranty. Low-iron glass lacks the green tint of standard glass, which shows off a planted tank.

On a rimless tank, choose a canister filter or a HOB with an adjustable leveler, and a light with mounting legs that grip a bare glass edge. See planted tank lights.