Stop Feeding by Instinct — Here's How to Calculate It

Feed is more than half of production cost. And every kilo left uneaten turns into ammonia and takes your water quality down with it. Guessing the feed amount loses you money and water simultaneously. Calculate, verify, adjust. ■ Step 1 — Calculate biomass Biomass = surviving count × average body weight Say you stocked 100,000 post-larvae and estimate 85% survival, leaving 85,000 animals. If a sample gives an average weight of 10 g: 85,000 × 10 g = 850,000 g = 850 kg Survival is an estimate, so keep correcting it against feed tray response and mortality records. ■ Step 2 — Multiply by the feeding rate for that size Feeding rate is daily feed as a percentage of biomass, and it falls as shrimp grow. Common guidance: 1–3 g — 8–6% of biomass 3–5 g — 6–5% 5–10 g — 5–4% 10–15 g — 4–3% 15–20 g — 3–2.5% Over 20 g — 2.5–2% For the example above (850 kg, average 10 g), applying 4%: 850 kg × 0.04 = 34 kg/day That is the daily total, normally split across 4–5 feedings. ■ Step 3 — Always verify with the feed tray The calculation is only a starting point. The real decision comes from the tray. Place 1–2% of each feeding in the tray and check after a set interval. Empty at 2 hours — underfed. Increase 5–10% from the next feeding. Emptied cleanly at 2–3 hours — correct. Hold. Feed still left after 3 hours — overfed. Cut 10–20%. ■ When to cut immediately, regardless of the calculation Water below 26°C, dissolved oxygen below 4 mg/L, a concentrated molting period, cloudy weather lasting more than two days, rising ammonia or nitrite, and any suspicion of disease. When shrimp are not eating, feeding to the calculation converts the entire ration into pollution. ■ Use FCR to check your management level Feed conversion ratio (FCR) = total feed used ÷ total weight gained 1.2–1.5 means you are managing well. Above 1.8 means either overfeeding or a wrong survival estimate. FCR is not only an end-of-cycle number — calculating it mid-cycle tells you whether your current management is right. ■ No records, no calculation Daily feed, leftovers, sample weights and mortality must all be recorded for the biomass estimate to be accurate — and only then does the calculation mean anything. Shrimp365 records these per tank and shows feeding trends alongside FCR.