125 gallon tank: dimensions & setup math
72 × 18 × 21 inches (L × W × H). Rounded planning dimensions; measure your tank.
125 nominal gal · about 1,372 lb with water, estimated glass and 2-inch gravel.
Estimated working water uses 85% of nominal: 106.25 US gal. The volume tool instead applies 85% to geometric volume. Neither is a measured fill.
Eight answers for this tank
- Tank volume
117.82 US gallons · 445.99 litres
- Gravel & substrate
150 lb gravel for a 2-inch bed
- Heater wattage
375–625 W planning range
- Filter flow
500–750 GPH for a community
- Stocking guide
1,296 in² surface · 72-inch swimming length
- Water changes
26.56 US gal for a 25% water change
- Dechlorinator dose
12.5 mL Prime for 125 US gal of new water
- Filled weight
About 1,372 lb filled (without stand)
Plan around this footprint
This 125 gallon plan uses 72 × 18 × 21 inches and 1,296 in² of floor. Compared with the 120 gallon (1,152 in²), its footprint is 12.5% larger. Large setup: plan hose access, independent temperature checks and a purpose-built stand before filling.
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.