Compare two tank sizes
Choose two tanks to see what changes for you: floor for the fish, height for the light, the length of the light and lid, and the weight, with both drawn at one scale. It opens on the 20 long against the 20 high.
20 gallon long or 20 gallon high: what changes for you
- Both are sold as 20 gallons, so the same heater and filter ratings apply.
- The 20 gallon long has 25% more floor (378 against 303 square inches): more room for bottom fish and for fish that swim the length of the tank.
- The 20 gallon high is 4 in taller: light from the rim has further to reach the plants, and you reach deeper to clean the bottom.
- The 20 gallon long is 6 in longer, so it takes a longer lid; the Fluval Plant 3.0 32W spans both.
| Fact | 20 gallon long | 20 gallon high |
|---|---|---|
| Sold as | 20 gallons | 20 gallons |
| Outside size, L × W × H | 30¼ × 12½ × 12¾ in | 24¼ × 12½ × 16¾ in |
| Floor | 378 square inches | 303 square inches |
| Empty weight | 25 lb | 25 lb |
| Lights that span it | Fluval Plant 3.0 32W, Fluval Plant 4.0 32W, hygger 957 Planted Aquarium Light 48W | Fluval Plant 3.0 32W, Fluval Plant 4.0 32W, hygger 957 Planted Aquarium Light 36W |
| Light at the plants | At least 120 PAR from a Fluval Plant 4.0 32W, 11 in above 2 in of gravel | At least 70 PAR from a Fluval Plant 4.0 32W, 15 in above 2 in of gravel |
| Example group | 8 neon tetras, 6 panda corydoras and a honey gourami. Check your own fish → | 8 ember tetras and 6 pygmy corydoras. Check your own fish → |
| Fish lists | Fish for a 20 gallon tank | Fish for a 20 gallon tank |
| Its own page | Plan a 20 gallon long tank → | Plan a 20 gallon high tank → |
Before you choose
The gallon label says little about the tank you live with. Floor sets how many bottom fish and fast swimmers fit; height sets how far the light reaches and how deep you reach to clean; length sets the light, the lid and the stand. The sizes here are the named maker’s outside dimensions, mostly Aqueon’s; another brand’s tank with the same label can differ, so check the model before you buy.
Every format at one scale · Standard aquarium sizes · Filled weight calculator · Plant light calculator