Our picks at a glance
- Best overall kitAqueon 20 Gallon LED Aquarium Kit
Complete, widely available kit with filter, heater and LED hood in a standard 20 high footprint.
- Best alternative kitTetra 20 Gallon Aquarium Kit
Comparable all-in-one package built around a Whisper filter and a heater, easy to find online.
- Best for fish and floor spaceAqueon Standard 20 Gallon Long
The 30 in length gives active schooling fish and bottom dwellers far more room than a tall tank.
- Best for planted aquascapesUNS 60U rimless aquarium
Low-iron glass and a clean rimless profile, sized for a 60 cm aquascape.
01
Why a 20 gallon is the best first aquarium
A 20 gallon aquarium sits in the sweet spot for beginners. Small tanks swing quickly in temperature and ammonia when something goes wrong, while a 55 gallon demands a heavy stand and bigger equipment. Twenty gallons (about 76 liters) dilutes mistakes, supports a real community of small fish and still weighs a manageable 200 to 225 lb filled.
It is also the first size where you can keep a proper school of tetras or rasboras, a group of corydoras and a centerpiece fish together. Our guide to the best fish for a 20 gallon tank lists stocking plans that work in both shapes. If your space is tighter, compare with our best 10 gallon aquarium picks.
Whatever you buy, plan the nitrogen cycle before buying fish. Our step-by-step guide on how to cycle a fish tank takes about 4 to 8 weeks and avoids most beginner losses.
02
Comparison table
The main split is between complete kits (fast, simple) and bare tanks (more choice, better long-term setups).
| Tank | Shape | Equipment included | Best for | Price |
|---|---|---|---|---|
| Aqueon 20 Gallon LED Kit | 20 high | Hood, LED, filter, heater | Beginners | $$ |
| Tetra 20 Gallon Kit | 20 high | Hood, LED, Whisper filter, heater | Beginners | $$ |
| Aqueon Standard 20 Long | 20 long | None | Community fish, shrimp | $ |
| UNS 60U | 60 cm rimless | None | Aquascaping | $$$ |
| SeaClear 20 Gallon | Rectangular acrylic | Varies by version | Light, durable setups | $$ |
| Aqueon Standard 29 | 30 in, tall | None | More volume, same footprint | $ |
Aqueon · Complete kit (20 high)
Aqueon 20 Gallon LED Aquarium Kit
Best for: First-time keepers who want everything in one box
Aqueon’s 20 gallon kit is one of the most common starter setups in US pet stores. It combines a 20 high glass tank with a low-profile LED hood, an Aqueon QuietFlow power filter, a preset submersible heater, a thermometer, fish food and a water conditioner sample. Everything is matched to the tank, which removes most of the guesswork for a beginner. The trade-offs are typical for kits: the included light is fine for fish and low-light plants but weak for demanding plants, and many keepers later upgrade the filter for extra capacity.
Pros
- Everything needed except substrate and decor
- Hood limits evaporation and jumping
- Easy to find in stores and online
- Standard size, so stands and replacement parts are easy to source
Cons
- Tall 20 high shape has a smaller footprint
- Stock light too weak for carpeting plants
- Preset heater cannot be fine-tuned
- Volume
- 20 US gal (about 76 L)
- Shape
- 20 high, about 24 x 12 x 16 in
- Included
- LED hood, filter, heater, thermometer
- Material
- Glass, black trim
Tetra · Complete kit (20 high)
Tetra 20 Gallon Aquarium Kit
Best for: Beginners comparing kits on price and availability
Tetra’s 20 gallon kit follows the same recipe as the Aqueon: a glass 20 high tank, a hood with LED lighting, a Tetra Whisper power filter with cartridges and a submersible heater. Whisper filters are simple and inexpensive to maintain, and the kit is a straightforward way to get a properly sized community tank running. As with any kit, the filter is designed for the nominal volume, so heavily stocked tanks or messy fish benefit from an extra sponge filter or a stronger hang-on-back unit.
Pros
- Complete starter package
- Simple cartridge filter maintenance
- Standard footprint fits common 20 gallon stands
Cons
- Cartridge costs add up over time
- Basic lighting
- Filter is only adequate for the nominal volume
- Volume
- 20 US gal (about 76 L)
- Shape
- 20 high, about 24 x 12 x 16 in
- Included
- LED hood, Whisper filter, heater
- Material
- Glass, black trim
Aqueon · Bare glass tank (20 long)
Aqueon Standard 20 Gallon Long
Best for: Schooling fish, corydoras, shrimp and keepers who choose their own gear
The 20 long is the shape many hobbyists prefer: 30 in long, 12 in wide and only 12 in tall. The same volume as a 20 high is spread over a longer, shallower footprint, which suits active schooling fish, bottom dwellers like corydoras and kuhli loaches, and plants that need light to reach the substrate. It is sold bare, so you choose the filter, heater, light and lid. That costs more planning but lets you build a better setup than most kits offer. Aqueon standard tanks are regularly discounted during big-box dollar-per-gallon sales.
Pros
- Best footprint for most community fish
- Shallow depth makes planting and maintenance easy
- Very affordable bare tank
- Huge choice of lids, stands and lights
Cons
- No equipment included
- Needs a 30 in stand or surface
- Lid sold separately
- Volume
- 20 US gal (about 76 L)
- Dimensions
- About 30 x 12 x 12 in (76 x 30 x 30 cm)
- Included
- Tank only
- Material
- Glass, black trim
Ultum Nature Systems · Rimless low-iron glass tank
UNS 60U rimless aquarium
Best for: Planted tanks and aquascapes on display
The UNS 60U is a 60 cm rimless cube-like tank made of low-iron (ultra-clear) glass, a standard size for nature-style aquascapes. At about 60 x 36 x 36 cm it holds roughly 20 gallons, with more depth front to back than a US 20 long, which helps create perspective in a layout. It comes with a leveling mat and no equipment, so it pairs best with a canister filter, an inline or submersible heater and a dedicated planted-tank light. It is a premium choice, and the open top means higher evaporation and a lid if you keep jumpers.
Pros
- Very clear low-iron glass
- Clean rimless look with polished edges
- Deeper footprint suits aquascaping
Cons
- No lid or equipment
- Higher price than standard tanks
- Open top increases evaporation
- Volume
- About 20 US gal (78 L)
- Dimensions
- About 60 x 36 x 36 cm (23.6 x 14.2 x 14.2 in)
- Included
- Tank and leveling mat
- Material
- Low-iron glass, rimless
SeaClear · Acrylic tank
SeaClear 20 Gallon Acrylic Aquarium
Best for: Keepers who want a lighter, impact-resistant tank
SeaClear acrylic tanks are a long-running US alternative to glass. Acrylic is much lighter, insulates slightly better and resists impacts, which makes it popular for kids' rooms, offices and setups that must be moved. SeaClear tanks have a top with cut-outs for equipment, and some versions ship as a system with a hood and light. The well-known downside of acrylic is that it scratches easily, so use an acrylic-safe algae pad and never let gravel get between the pad and the panel. It must also sit on a fully flat, supportive surface.
Pros
- Lightweight and impact resistant
- Good clarity when kept clean
- Top frame with built-in openings
Cons
- Scratches easily
- Needs full bottom support
- Usually costs more than an equivalent glass tank
- Volume
- 20 US gal (about 76 L)
- Shape
- Rectangular, several versions
- Included
- Tank (system versions add hood and light)
- Material
- Acrylic
Aqueon · Bare glass tank (step-up option)
Aqueon Standard 29 Gallon
Best for: Keepers who have a 30 in spot and want more margin
If you are shopping for a 20 long, look at the 29 gallon as well. It shares the same 30 x 12 in footprint, so it fits the same stand and lids, but at 18 in tall it holds about 45% more water. More volume means more stable temperature and water quality, and room for a dwarf gourami or a slightly larger school. The extra height makes planting a bit harder and suits fish that use the water column. It is a bare tank, so budget for the full equipment list.
Pros
- Same footprint as a 20 long
- More stable volume
- Inexpensive per gallon
Cons
- Taller, harder to reach the bottom
- Heavier when filled
- Bare tank, no equipment
- Volume
- 29 US gal (about 110 L)
- Dimensions
- About 30 x 12 x 18 in (76 x 30 x 46 cm)
- Included
- Tank only
- Material
- Glass, black trim
03
How we chose these tanks
This is an editorial selection, not a hands-on lab test. Tanks were chosen on manufacturer-declared dimensions and contents, glass or acrylic quality, availability in US stores and on Amazon, the cost of completing the setup, and how consistently each model is recommended in established hobby communities. We left out kits whose specifications are unclear or that are hard to find in the US.
04
20 high vs 20 long: which shape should you buy?
Both hold the same volume, but they are not interchangeable. The 20 long (30 x 12 x 12 in) has 25% more floor area. Fish swim horizontally, and bottom dwellers like corydoras need ground, so the long version is the better default for community tanks, shrimp colonies and carpeting plants.
The 20 high (24 x 12 x 16 in) fits a shorter surface and gives more vertical room, which suits taller-bodied fish and stem plants. Most kits use this shape. It is a perfectly good tank, but plan for fish that use the middle water column, and avoid long-finned species that need length to cruise.
| Shape | Footprint | Height | Strengths |
|---|---|---|---|
| 20 long | 30 x 12 in | 12 in | Swimming length, bottom space, easy planting |
| 20 high | 24 x 12 in | 16 in | Fits smaller furniture, more vertical room |
| 60 cm rimless (UNS 60U) | About 24 x 14 in | About 14 in | Depth for aquascapes, premium look |
05
Buying guide: what to check before you buy
Add a substrate suited to your plans (our best aquarium substrate guide covers gravel, sand and plant soils), a test kit and a water conditioner before the tank is filled.
- Kit or bare tank: a kit saves time; a bare tank lets you pick a better filter, heater and light from the start.
- Filtration: aim for a filter rated for at least the tank volume, ideally more. Compare options in our best aquarium filter and best HOB filter guides.
- Heating: tropical fish need a stable 75–80 °F (24–27 °C). A 75 to 100 W adjustable heater suits most 20 gallon tanks; see our best aquarium heater review.
- Lighting: stock kit lights grow easy plants such as java fern and anubias. For carpets or red plants, check our best aquarium light picks.
- Lid: a hood or glass lid limits evaporation and stops jumpers such as hatchetfish and some killifish.
- Stand: a filled 20 gallon weighs over 200 lb. Use a stand rated for aquariums, level and fully supported.
06
How to choose by use
A 20 gallon is also a good home for a betta fish with a small peaceful community, as long as the filter output is gentle. For pairing ideas, see betta tank mates.
| Setup | Recommended pick | Why |
|---|---|---|
| First community tank | Aqueon 20 Gallon LED Kit | Complete, matched equipment |
| Tetras, rasboras, corydoras | Aqueon Standard 20 Long | Swimming length and floor space |
| Planted aquascape | UNS 60U | Clear glass, depth, rimless look |
| Shrimp colony | Aqueon Standard 20 Long | Large bottom area, add a sponge filter |
| Kids' room or office | SeaClear 20 Gallon | Light and impact resistant |
| Single betta with tank mates | Aqueon 20 Gallon LED Kit | Hood stops jumping, gentle flow possible |
07
Common mistakes with 20 gallon tanks
If you are setting up your very first tank, our beginner aquarium guide walks through the full order of operations, from rinsing substrate to the first fish.
- Adding all the fish at once. Stock gradually over several weeks after cycling so the bacteria can keep up.
- Choosing fish that outgrow the tank. Common plecos, oscars, goldfish and most cichlids need far more than 20 gallons.
- Trusting the kit filter for a heavy stock. Add a sponge filter or upgrade if you keep many fish or messy feeders.
- Placing the tank in direct sun or by a heater vent. Both cause algae blooms and temperature swings.
- Skipping a level check. An uneven stand stresses the seams; use a level before filling.
Frequently asked questions
Frequently asked questions
What is the best 20 gallon aquarium for beginners?
The Aqueon 20 Gallon LED Aquarium Kit is the easiest choice because it includes a hood, LED light, filter and heater sized for the tank. If you are comfortable picking your own equipment, a bare Aqueon 20 Long offers a better footprint for most community fish at a lower tank price.
Is a 20 long or a 20 high better?
For most fish, the 20 long is better: it is 30 in long with 25% more floor area, which suits schooling fish, corydoras, shrimp and plants. The 20 high takes less wall space and offers more height, so it works when your furniture is only 24 in wide or for fish that use the mid-water.
How much does a 20 gallon fish tank weigh when full?
Water alone weighs about 167 lb for 20 gallons. With glass, substrate, rocks and equipment, a filled 20 gallon usually reaches 200 to 225 lb. Use a stand or furniture rated for that weight, keep it level and avoid particleboard pieces that sag over time.
How many fish can go in a 20 gallon aquarium?
It depends on adult size and behavior rather than a strict inch-per-gallon rule. A typical plan is one school of 8 to 10 small tetras or rasboras, 6 corydoras and a centerpiece such as a honey gourami. Stock slowly and test water weekly at first.
Do I need a heater in a 20 gallon tank?
Yes for tropical fish, which need a stable 75–80 °F (24–27 °C). A 75 to 100 W adjustable heater suits most 20 gallon tanks. Coldwater species such as white cloud minnows can go without one if your room stays in their range.
Sources and references
Written and reviewed by the handsoffmyhobby editorial team according to our editorial policy.
