Both tanks are sold as 20 gallons and hold about the same water, but they're shaped very differently. The 20 gallon long is long and low; the 20 gallon high is shorter and taller.

Dimensions and footprint

20 gallon long20 gallon high
Dimensions (L x W x H)30 x 12 x 12 in24 x 12 x 16 in
Footprint360 sq in (2.5 sq ft)288 sq in (2.0 sq ft)
Water weightabout 167 lbabout 167 lb
Gravel for 2 in bedabout 42 lbabout 33 lb
Stand needed30 x 12 in24 x 12 in

Typical standard sizes. Check your tank's label; brands vary slightly.

When to pick the 20 long

  • Active swimmers such as danios and small rasboras, which use length more than height
  • Bottom dwellers like corydoras, kuhli loaches and dwarf crayfish, which use floor space
  • Shrimp tanks and low-tech planted tanks, where light needs to reach the bottom
  • Easy maintenance: you can reach every corner without getting your shoulder wet

It also shares a footprint with the 29 gallon, so you can upgrade later without a new stand footprint. See 20 long vs 29 gallon.

When to pick the 20 high

  • Your space is only 24 inches wide
  • You want tall plants or a tall rock or driftwood centrepiece
  • You keep fish that use the middle and top of the water

The verdict

For most first community tanks, the 20 long is the more flexible choice. Pick the 20 high when space is tight or the display height matters more than floor area. Either way, the substrate calculator will tell you how much gravel to buy.

Frequently asked questions

Is a 20 long or 20 high better?

For most fish, the 20 long. Its extra 6 inches of length and larger footprint give more swimming room and floor space. The 20 high suits tall plants or a small space.

What are the dimensions of a 20 gallon high tank?

A standard 20 high measures about 24 x 12 x 16 inches. The 20 long measures about 30 x 12 x 12 inches.

Do the 20 long and 20 high weigh the same?

Nearly. Both hold about 20 gallons, around 167 lb of water. The 20 long needs a little more gravel because its floor is larger.