AquariumCalcs: Fin & Figures — for the fish aficionado
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20 Gallon Aquarium Dimensions (High & Long)

Standard 20-gallon tank dimensions for both the High and Long variants, filled weight, and stand notes.

MeasurementValue
20 Gallon High24 × 12 × 16 in, ≈ 225 lb filled
20 Gallon Long30 × 12 × 12 in, ≈ 225 lb filled
Same volume, different shapeBoth hold 20 gallons, but the High is taller and narrower (better for tall plants and upper-swimming fish); the Long is longer and shallower (generally the better stocking footprint, a favorite for planted low-tech setups).

Nominal vs. actual dimensions

Tank dimensions are generally accurate to the glass, but always double-check against your specific manufacturer, since trim, rim style, and glass thickness can shift the outer dimensions by a small margin. Filled weight includes the tank, water, substrate, and decor -- confirm your stand and floor can support it before filling.

Source: Standard, widely-used US aquarium industry dimensions for this tank size.

Frequently asked questions

Are these dimensions exact for every brand?

They're standard for this size, but always confirm against your specific tank's manufacturer, since trim and rim style can vary slightly between brands.

Does filled weight include the stand?

No -- this is the tank itself, filled with water, substrate, and decor. Check your stand's own weight rating separately, and see our Stand & Floor Load Calculator for a fuller picture.

Can I use a smaller stand than this tank's footprint?

Not recommended -- a stand should fully support the tank's footprint; an undersized stand risks instability, especially once the tank is filled and heavy.

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