Pond Volume
4,488 gal
Max Fish
17
Pump (GPH)
4,489
Liner
500 sq ft
Pond Volume
4,488 gal
600 cu ft
Max Koi
17
Pump Size
4,489 GPH
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Inputs
Result
Volume = 15 × 10 × 4 × 7.48 = 4,488 gal. Max koi = 4,488/250 = 17. Pump = 4,488 GPH. Liner = (15+8+2)×(10+8+2) = 25×20 ft.
Inputs
Result
Volume = 8 × 6 × 2 × 7.48 = 718 gal. Max goldfish = 718/20 = 35. Liner = (8+4+2)×(6+4+2) = 14×12 ft.
For rectangular ponds: Length × Width × Average Depth × 7.48 = gallons. A 15×10×4 ft pond holds about 4,488 gallons. Irregular shapes should use 80% of the rectangular volume as an estimate.
Stocking rates vary dramatically by species. Koi need 250 gallons per fish, goldfish 20 gallons, tilapia 50 gallons, and catfish 75 gallons. Overstocking leads to poor water quality and fish disease.
| Species | Gal/Fish | 1,000 Gal Pond | 5,000 Gal Pond |
|---|---|---|---|
| Koi | 250 | 4 fish | 20 fish |
| Goldfish | 20 | 50 fish | 250 fish |
| Tilapia | 50 | 20 fish | 100 fish |
| Catfish | 75 | 13 fish | 66 fish |
The pump should circulate the entire pond volume once per hour. A 4,500 gallon pond needs a 4,500 GPH pump. For ponds with heavy fish loads, size up 25–50%. Head height (distance water must be lifted) reduces effective flow.
Liner size = (Length + 2×Depth + 2 ft overlap) × (Width + 2×Depth + 2 ft overlap). A 15×10×4 ft pond needs about a 25×18 ft liner. EPDM rubber liner (45 mil) is the gold standard for durability.
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Last Updated: Mar 19, 2026
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