- Calculate daily feed per active planted area.
- Use a named reference range without universalizing it.
- Plan staggered crops while respecting fish capacity.
Feed-to-area planning calculator
Feed g/day = biomass kg × 1,000 × ration% ÷ 100. Area = feed ÷ selected ratio.
Calculated feed (g/day): 180; Current ratio (g/m²/day): 60; Area at selected ratio (m²): 3; Feed for entered area (g/day): 180
60 g/m²/day is an example at the low end of the SRAC 454 (UVI) raft design range of 60–100. Ration and ratio are editable planning assumptions. This does not calculate safe fish stocking or biofilter capacity.
01 / Begin with the feed stream
Aquaponic nutrient supply begins largely with feed. Some becomes fish growth, some leaves as solids and some enters dissolved pathways. A feed-to-area ratio is a planning relationship within a particular treatment and crop system, not a universal conversion of fish into vegetables.
SRAC 454, the University of the Virgin Islands raft-system publication, gives a design feeding-rate ratio of 60–100 g feed per m² of raft growing area per day, using the low end for small plants such as Bibb lettuce and the high end for larger plants such as romaine or Chinese cabbage; SRAC 5007, the small-scale principles publication hosted by OSU, restates it as 2–4 oz of feed per 10 ft² of plants, printed there as 56–100 g/m²/day. Use this only as a named system reference. Media beds, crop types, feed composition, mineralization and environmental conditions change how an area responds.
Reading: Aquaponics—Integrating Fish and Plant Culture (SRAC 454) ↗ · Principles of Small-Scale Aquaponics (SRAC 5007) ↗
02 / Work the balance in both directions
Choose 60 g/m²/day as an illustrative point within that cited range. A measured 180 g/day feed input corresponds to 180 ÷ 60 = 3 m² of planted area at that chosen ratio. Conversely, 5 m² at 60 g/m²/day corresponds to 300 g/day feed.
These are arithmetic relationships. They do not authorize feeding more than fish can consume or stocking enough fish to force a target ratio. If the existing fish safely consume only 180 g/day, begin with the area and crops that work at that input, or consider a deliberately decoupled plant system.
| Daily feed | Selected planning ratio | Calculated area |
|---|---|---|
| 120 g/day | 60 g/m²/day | 2 m² |
| 180 g/day | 60 g/m²/day | 3 m² |
| 300 g/day | 60 g/m²/day | 5 m² |
03 / Balance over the crop cycle
Measure planted area actually in production, not the greenhouse floor or empty channels. Young seedlings and nearly harvested canopies have different nutrient demand. Stagger plant batches so a whole-bed harvest does not suddenly remove most uptake.
Log feed, fish biomass, planted area, crop stage, purge volume, top-up and harvest. Observe nitrate trends and plant quality over time. Rising nitrate can indicate input exceeding uptake, but concentration also changes with water replacement and volume.
- Weigh daily feed and calculate the average over a representative stable interval.
- Measure active planted area and list crop cohorts.
- Choose and document a source-specific comparison ratio; calculate current g/m²/day.
- Check TAN, nitrite, nitrate, oxygen, pH and alkalinity alongside the area calculation.
- Adjust crop scheduling or system design within fish welfare and treatment limits; verify the response before expanding.
Reading: Aquaponics—Integrating Fish and Plant Culture (SRAC 454) ↗
04 / Nitrogen is not the whole nutrient solution
An adequate nitrate trend does not establish potassium, calcium, iron or other nutrients at the crop’s required availability. Solids handling and alkalinity management influence the balance. Diagnose suspected deficiencies with water, plant and system evidence before adding supplements.
Do not use the hydroponic fertilizer calculator to dose the coupled fish system. Its recipes were not formulated as fish-safe additions. The plant-nutrition chapter shows how to separate mass arithmetic from product suitability.
FIELD QUESTIONA larger bed lowers calculated feed per m². Has the system become safer for fish?
The ratio changed, but fish oxygen and waste-processing requirements may be unchanged. Planted area is not a substitute for verified aeration and filtration capacity.
Reading: Important Water Quality Parameters in Aquaponics Systems (CR680) ↗
Parts & buying criteria
Build your own parts & cost worksheet →
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.
Check size, materials and operating conditions with your chosen supplier before ordering.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.
Check size, materials and operating conditions with your chosen supplier before ordering.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.
Check size, materials and operating conditions with your chosen supplier before ordering.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.
Check size, materials and operating conditions with your chosen supplier before ordering.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.
Check size, materials and operating conditions with your chosen supplier before ordering.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.
Check size, materials and operating conditions with your chosen supplier before ordering.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.
- Southern Regional Aquaculture Center · hosted by OSU ExtensionAquaponics—Integrating Fish and Plant Culture (SRAC 454) ↗
Tank-to-treatment-to-growing-to-sump layout and production tradeoffs.
- Southern Regional Aquaculture Center · hosted by OSU ExtensionPrinciples of Small-Scale Aquaponics (SRAC 5007) ↗
Design, media-bed depth, biofilter sizing and aeration, potassium/calcium/iron supplementation and the UVI feed-to-area rule restated in ounces per square foot; applicability depends on system.
- New Mexico State University ExtensionImportant Water Quality Parameters in Aquaponics Systems (CR680) ↗
Fish-system water chemistry, oxygen, temperature and nitrification.
The next useful connections.
Reservoir management and solution replacement
Use a water-and-nutrient ledger to distinguish top-ups, rebalancing and a complete batch change.
Interactive tool · 6 min + guided practice →Fish & feedingFeeding, biomass and stocking
Use fish mass and actual feed intake as operating inputs, with capacity checked independently.
Interactive tool · 6 min + guided practice →Plants & growing mediaPlant nutrition in a fish-connected system
Diagnose crop needs while accounting for feed, water, pH and the fish living in the same solution.
6 min + guided practice →