Calculator
Enter your pond details to estimate biomass, density, and feeding.
Example data table
| Pond volume | Fish count | Avg weight | Survival | Biomass | Density | Feed/day |
|---|---|---|---|---|---|---|
| 2,000 L | 120 | 35 g | 92% | 3.864 kg | 1.932 kg/m³ | 0.077 kg |
| 800 gal | 220 | 2.4 oz | 90% | 13.472 kg | 4.447 kg/m³ | 0.269 kg |
| 3.0 m³ | 400 | 18 g | 95% | 6.840 kg | 2.280 kg/m³ | 0.137 kg |
| 1,200 L | 90 | 70 g | 98% | 6.174 kg | 5.145 kg/m³ | 0.154 kg |
| 500 gal | 60 | 6.0 oz | 85% | 8.669 kg | 4.579 kg/m³ | 0.173 kg |
Values shown are illustrative and depend on your inputs.
Formula used
- Effective fish count = Fish count × (Survival % ÷ 100)
- Biomass (kg) = Effective count × Average weight (g) ÷ 1000
- Volume (m³) converts from L or gallons to cubic meters
- Stocking density (kg/m³) = Biomass ÷ Volume (m³)
- Daily feed (kg/day) = Biomass × (Feed rate % ÷ 100)
- Projected weight uses SGR: Wt = W0 × e^((SGR ÷ 100) × Days)
- Total feed approximates using average biomass over the period
How to use this calculator
- Measure water volume after media and displacement are considered.
- Count fish or estimate from batches and recent harvest notes.
- Weigh a representative sample to get an average weight.
- Set survival rate based on your recent observations.
- Choose a feed rate that matches size and temperature.
- Optional: add days and SGR for a growth projection.
- Review density warnings and adjust stocking or volume.
- Download CSV or PDF to keep production records.
Biomass as a planning metric
Biomass converts a pond snapshot into a working production number. The calculator adjusts fish count by survival, then multiplies by average weight to estimate live weight in kilograms. Sample 10–20 fish for an average you can repeat. This beats “number of fish” because 150 fingerlings at 20 g equal 3 kg, while 150 fish at 120 g equal 18 kg.
Volume and density benchmarks
Stocking density is displayed as kg per cubic meter, with automatic conversion from liters or US gallons. Density helps you compare systems of different shapes and sizes. Many garden ponds operate around 5–20 kg/m³ with steady aeration and solids control. Set a density limit to trigger a warning before oxygen demand and waste load outpace your filtration.
Feeding tied to standing biomass
Feed demand should follow biomass, not the calendar. Enter a daily feed rate as a percent of biomass. A 2.0% setting means 10 kg biomass needs 0.20 kg feed per day; at 3.0% it becomes 0.30 kg. Start lower in cool water, then adjust with appetite. Split rations into two to four meals to reduce waste.
Growth projection for harvest timing
The projection uses specific growth rate (SGR) to estimate future average weight: Wt = W0 × e^((SGR/100)×days). Typical SGR often falls near 0.5–2.0%/day, depending on temperature and oxygen. With 35 g fish, 1.0%/day over 60 days projects about 64 g. With 92% survival and 120 fish, projected biomass approaches 7.1 kg for planning.
Using exports for management decisions
Export CSV or PDF after grading, partial harvests, or temperature shifts. Track density, daily feed, and notes alongside water tests. If ammonia rises after increasing feed, reduce the percentage, improve aeration, or lower density. Use the total-feed estimate to budget pellets and storage; compare expected consumption to delivery schedules midseason, and adjust to avoid spoilage costs. This supports harvest timing and steadier plant growth overall.
FAQs
1) What does the calculator mean by biomass?
Biomass is the total live weight of fish in the pond. It is calculated from effective fish count (after survival) multiplied by average fish weight, then converted to kilograms.
2) How do I choose an average fish weight?
Net a small, calm sample and weigh 10–20 fish. Divide total weight by the number weighed. Recheck after grading or when temperature changes, because appetite and growth rate shift.
3) Why is stocking density shown in kg/m³?
Kg per cubic meter standardizes comparisons across ponds and tanks. It links directly to oxygen demand, waste production, and filtration load, so it is a practical indicator for system limits.
4) What is a reasonable daily feed rate?
Many growers start near 0.5–2.0% of biomass for larger fish, and 2–4% for smaller fish in warm water. Adjust based on consumption, water tests, and uneaten feed.
5) How should I use SGR for projections?
Enter an SGR that matches your conditions. Cooler water and lower oxygen reduce SGR, while warm, well‑aerated systems increase it. Use projections as planning estimates, then update with new sample weights.
6) Do the CSV and PDF exports include my inputs?
Yes. After you calculate, the export buttons create a report with your key inputs and outputs, including biomass, density, feed estimates, projections, and notes. Save exports to build a season‑long record.