Aquarium Forge

20 gallon High Aquarium

Everything about the 20 gallon High tank: its real water volume, the fish that fit, and the heater, filter, substrate, and total weight it needs — calculated with the same tools as our calculators.

Quick Facts

Nominal Volume
20 US gallons (75.71 L)
Approximate Water Volume
17–19 gallons
Common Dimensions
24 × 12 × 16 inches
Suitable Fish
40 species in our database
Recommended Heater
75 W
Recommended Filter
80 GPH (303 LPH)

Suitable Fish

These species have a minimum tank requirement of 20 gallons or less, so they can live in a 20 gallon High tank:

Stocking Examples

A balanced starting point for a 20 gallon High community — 8 × Neon Tetra + 1 × Honey Gourami.

Stocking status: Moderate — Bioload 14 of ~20 points for your 20-gallon tank.

Build your own plan

Filter Recommendations

For a freshwater community, target about 80 GPH (303 LPH) of actual turnover. The minimum sensible flow is 60 GPH.

Manufacturer flow is rated on an empty filter — real flow drops with media and head height, so choose toward the upper end.

Heater Requirements

Holding 78°F in a 68°F room needs roughly 75 W. A temperature rise of 10°F (5.6°C) is assumed.

Two smaller heaters (one at each end) heat more evenly and give redundancy — worth considering for larger tanks.

Substrate Amount

With a 2-inch gravel bed, a 20 gallon High tank needs about 9.44 L / 576 cu in — roughly 15.86 kg / 34.96 lb.

Estimated Weight

Set up and filled, a 20 gallon High tank weighs around 201.49 lb — including water, glass, a 2-inch gravel bed, and a small allowance for decor and equipment.

Add the stand or cabinet weight separately when checking your floor.

Compatible Equipment

  • Heater: 75 W (adjust for your room temperature).
  • Filter: 80 GPH (303 LPH) actual turnover.
  • Substrate: 9.44 L / 576 cu in of gravel at a 2-inch depth.
  • Lighting: match the fixture to the tank length (24 inches) and to your plants' needs.
  • Stand: rated for at least 201.49 lb.

Frequently asked questions

How many gallons does a 20 gallon High aquarium actually hold?

A 20 gallon High tank is rated at 20 US gallons nominal, but real water volume runs lower — typically 17–19 gallons once it is filled to the frame line and you account for substrate, rock, and equipment displacement.

What fish can live in a 20 gallon High tank?

Roughly 40 of the species in our database suit a 20 gallon High tank (minimum tank requirement at or below 20 gallons). Popular options include Betta, Neon Tetra, Guppy, Bronze Corydoras, Harlequin Rasbora.

What filter do I need for a 20 gallon High tank?

For a freshwater community, aim for about 80 GPH (303 LPH) of actual turnover — the minimum sensible flow is 60 GPH. Manufacturer ratings are measured on an empty filter, so size up when in doubt.

What heater wattage for a 20 gallon High tank?

To hold 78°F in a 68°F room, a 20 gallon High tank typically wants around 75 W. The exact figure depends on the temperature rise and how cold the room gets.

How much gravel does a 20 gallon High tank need?

With a 2-inch bed, a 20 gallon High tank needs about 9.44 L / 576 cu in, weighing roughly 15.86 kg / 34.96 lb.

Figures are planning estimates calculated at 68°F room → 78°F target, 90% fill, and a 2-inch gravel bed. Last reviewed: .