20 gallon long tank: dimensions & setup math
30 × 12 × 12 inches (L × W × H). Rounded planning dimensions; measure your tank.
20 nominal gal · about 232.65 lb with water, estimated glass and 2-inch gravel.
Estimated working water uses 85% of nominal: 17 US gal. The volume tool instead applies 85% to geometric volume. Neither is a measured fill.
Eight answers for this tank
- Tank volume
18.7 US gallons · 70.79 litres
- Gravel & substrate
41.67 lb gravel for a 2-inch bed
- Heater wattage
60–100 W planning range
- Filter flow
80–120 GPH for a community
- Stocking guide
360 in² surface · 30-inch swimming length
- Water changes
4.25 US gal for a 25% water change
- Dechlorinator dose
2 mL Prime for 20 US gal of new water
- Filled weight
About 232.65 lb filled (without stand)
Plan around this footprint
This 20 gallon long plan uses 30 × 12 × 12 inches and 360 in² of floor. Compared with the 20 gallon high (288 in²), its footprint is 25% larger. Small setup: leave an open swimming lane and add livestock in stages after the filter is cycled. The 20 long has a 30 × 12-inch floor versus 24 × 12 for the 20 high: 25% more substrate at the same depth, despite the same nominal capacity.
Dimensions and limits
Aqueon size chart. Listed dimensions are representative, not exact catalog measurements. Names identify marketed sizes; geometry explains why the calculated gallons can differ. Weight excludes the stand, rocks and equipment.