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Fish Tank Volume Calculator
Enter your aquarium dimensions and get volume (gallons + liters), loaded weight, filter flow rate, heater wattage, glass thickness, and stocking capacity. Supports rectangular, bowfront, cylinder, and hexagon tank shapes.
Water volume
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- Gross volume
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- Net (with substrate)
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- Liters
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- Loaded weight
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Equipment sizing
Based on type, target temp, and tank size.
- Filter flow (GPH)
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- Turnover/hr target
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- Heater wattage
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- Min glass thickness
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- Substrate (lb dry)
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- Surface area (sq in)
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Stocking capacity
Conservative inch-per-gallon and bioload-per-surface-area guidelines.
- Inches of fish (max)
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- Small community fish (e.g. tetras)
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- Medium (e.g. cichlids)
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Common-sense disclaimers
These are baseline guidelines from common aquarium-hobby references. Actual stocking depends on fish behavior, territory, and filtration headroom — not just inches. Always cycle a new tank for 4-6 weeks before adding livestock, and research individual species needs before stocking.
Volume math by tank shape
Rectangular: L × W × H ÷ 231 = gallons (231 cu in per gallon).
Bowfront: rectangular volume + bow area (approximated as a half-ellipse).
Cylinder: π r² × H ÷ 231.
Hexagon: 3√3/2 × s² × H ÷ 231, where s is side length (flat-to-flat = 2s × cos 30°).
Cube: side³ ÷ 231.
Half-moon: half of a cylinder of equivalent dimensions.
Common aquarium sizes
| Tank | Dimensions | Gallons | Loaded weight |
|---|---|---|---|
| 10 gal "starter" | 20 × 10 × 12 | 10 | ~110 lb |
| 20 gal high | 24 × 12 × 16 | 20 | ~225 lb |
| 29 gal | 30 × 12 × 18 | 29 | ~330 lb |
| 55 gal | 48 × 13 × 21 | 55 | ~625 lb |
| 75 gal | 48 × 18 × 21 | 75 | ~850 lb |
| 125 gal | 72 × 18 × 23 | 125 | ~1,400 lb |
| 180 gal | 72 × 24 × 25 | 180 | ~2,000 lb |