- Calculate biomass and a source-selected ration.
- Record actual feed intake and changes.
- Separate nutrient balance from safe carrying capacity.
Feed-to-area planning calculator
Feed g/day = biomass kg × 1,000 × ration% ÷ 100. Area = feed ÷ selected ratio.
60 g/m²/day is an example within OSU’s cited UVI raft range of 56–100. Ration and ratio are editable planning assumptions. This does not calculate safe fish stocking or biofilter capacity.
01 / Fish count is not load
Ten small fingerlings and ten harvest-size fish impose different demands. Estimate biomass as fish count × representative average mass, then update as fish grow, are removed or die. The daily feed input is a useful link to waste production and plant nutrients.
Feeding percentage depends on species, size, temperature, feed and health. Use the supplier’s feeding table and observed appetite. The calculator’s example percentage is an editable scenario, not a ration prescribed for all fish.
Reading: Principles of Small-Scale Aquaponics ↗ · Fish Health Management Considerations in Recirculating Aquaculture Systems—Part 1 ↗
02 / Calculate a ration transparently
For an example biomass of 12 kg and a selected daily ration of 1.5% body mass, planned feed is 12 × 1,000 × 0.015 = 180 g/day. Split feeding and pellet size according to the stock’s needs. Record what was actually offered and what remained uneaten.
A 20% biomass increase at the same feed percentage raises the daily feed by 20%. The biofilter, oxygen supply and solids handling must keep up even when the tank still looks uncrowded. Do not treat a nominal litre-per-fish rule as a carrying-capacity calculation.
| Input | Example | How to verify |
|---|---|---|
| Number of fish | 60 | Stock and mortality/harvest records. |
| Average mass | 0.2 kg | Representative, low-stress sampling plan. |
| Estimated biomass | 12 kg | Count × mean mass. |
| Selected ration | 1.5% / day | Species, size and temperature guidance. |
| Calculated feed | 180 g/day | Weigh offered feed and record response. |
03 / Observe every feeding
Watch fish before feeding: distribution, respiration, swimming and response to your presence. Offer the planned ration while observing acceptance. A sudden appetite drop is a water-quality or health signal, not an instruction to leave more pellets in the tank.
Remove uneaten feed using a method appropriate to the tank. Check oxygen, temperature, TAN and nitrite when appetite changes or feed load rises. Keep feed sealed, dry and within its use period; label open dates and lots.
- Review current biomass and the applicable feeding table.
- Weigh the ration before feeding and observe fish behavior.
- Record actual consumption and remove uneaten material.
- Adjust to measured conditions and specialist/supplier guidance; investigate abnormal refusal.
- Update biomass after grading or harvest and repeat water-quality checks after loading changes.
Reading: Seven rules of thumb to follow in aquaponics ↗ · Fish Health Management Considerations in Recirculating Aquaculture Systems—Part 3 ↗
04 / Stocking requires several independent checks
Fish capacity is constrained by oxygen delivery, carbon dioxide removal, ammonia conversion, solids removal, water circulation, space, welfare and emergency resilience. Surface area advertised for a filter is not a guarantee of processing at your temperature and feed load.
Keep a design record of maximum intended daily feed and the component capacities supporting it. Increase load in steps with measured response. When harvest removes fish, expect feed and nutrient inputs to decrease; adjust planted area and succession rather than compensating with overfeeding.
FIELD QUESTIONIf tank volume doubles, can fish biomass safely double?
Not automatically. Oxygen, filtration, flow, feed handling and backup capacity must also support the new load under actual operating conditions.
Reading: Fish Health Management Considerations in Recirculating Aquaculture Systems—Part 1 ↗
Parts & buying criteria
Showing aquaponic raft system. Quantities describe the teaching model. Specify real working volume, support, fittings and instruments for your installation.
01Fish tank1 · illustrated quantity+
Houses fish and receives the pumped return. Feed is an input to this living system.
Inspect: The fish are generic silhouettes, with no species or stocking-rate recommendation. Cutaway reveals the tank interior.
Maintain: Observe behavior and feeding response; keep a record of water tests and changes.
Smooth accessible tank, secure cover and species-appropriate volume determined by an aquaculture design.
Supplier links can be added by the publisher. The criteria stand independently.02Solids separator1 · illustrated quantity+
Intercepts settleable waste before it accumulates in later treatment and growing components.
Inspect: Open the front of the vessel. Brown particles beneath the central baffle represent collected waste, not a settling simulation.
Maintain: Inspect accumulation and remove it on an observation-based schedule without flushing it into the growing bed.
Accessible waste drain, removable internals and a design matched to expected solids and flow.
Supplier links can be added by the publisher. The criteria stand independently.03Biological filter1 · illustrated quantity+
Provides wetted surface for nitrifying organisms. This teaching layout shows a separate biofilter.
Inspect: The blue carriers indicate surface area; cyan flow does not measure nitrification or oxygen availability.
Maintain: Protect the established community during service. Verify nitrogen readings before and after changing loading or equipment.
Media and aeration matched to the intended feed load, water conditions and an independently reviewed design.
Supplier links can be added by the publisher. The criteria stand independently.04Raft growing bed1 · illustrated quantity+
Holds plants above water after solids handling and biofiltration. Roots hang below the raft.
Inspect: Compare the depth of this growing section with the shallow channels in the hydroponic lesson.
Maintain: Keep drains accessible and inspect root congestion. Remove crop debris without sending it downstream.
Cleanable bed, supported raft, access to drains and a root-zone aeration plan.
Supplier links can be added by the publisher. The criteria stand independently.05Sump & return pump1 · illustrated quantity+
Collects gravity drainage and pumps water to the fish tank, closing this particular circuit.
Inspect: This is the lowest collection point. The tank, filters and bed have progressively lower illustrative water levels.
Maintain: Check sump level, intake and leaks. Test whether drainage can be contained when power stops.
Usable reserve volume, pump service access, level protection and verified delivery at the required head.
Supplier links can be added by the publisher. The criteria stand independently.06Air supply1 · illustrated quantity+
A separate air pump supplies diffusers to the fish tank, biofilter and growing bed.
Inspect: White bubbles indicate air delivery only; bubble count is not a dissolved-oxygen reading.
Maintain: Check air lines, diffusers and backup arrangements. Verify oxygen with suitable measurement.
Airflow at operating depth, compatible diffusers and resilience reviewed for the living load.
Supplier links can be added by the publisher. The criteria stand independently.Evidence beside the lesson.
Source checks: September 2026. The geometry, inspection exercises and worksheets are original teaching material. The named organizations have not endorsed or reviewed this site.
Published recipe rates and planning ranges retain their source context. Calculator equations are accounting tools; they do not predict uptake, yield, toxicity or safe stocking. Model dimensions, water speeds, roots and fish counts are illustrative. Verify species, crop, source water and product labels for a real system.
- Oklahoma State University ExtensionPrinciples of Small-Scale Aquaponics ↗
Design and the UVI raft feed-to-area range; applicability depends on system.
- University of Florida IFAS ExtensionFish Health Management Considerations in Recirculating Aquaculture Systems—Part 1 ↗
RAS treatment capacity and startup.
- Food and Agriculture Organization of the United NationsSeven rules of thumb to follow in aquaponics ↗
Water-quality monitoring, feeding, stocking and production balance.
- University of Florida IFAS ExtensionFish Health Management Considerations in Recirculating Aquaculture Systems—Part 3 ↗
Biosecurity, quarantine, health monitoring and diagnosis.
The next useful connections.
Choose viable fish: temperature, feed and purpose
Compare six practical fish groups, then narrow them by your actual water conditions and a verified hatchery plan.
Interactive tool · 6 min + guided practice →Cycling & water balanceBalance fish feed and planted area
Turn feed grams per day into a transparent area comparison, then check the biological and hydraulic limits.
Interactive tool · 6 min + guided practice →