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Aquaponics Fish-to-Plant Ratio Calculator

Size your aquaponics grow bed area to match your fish stock's feeding rate, using the real published UVI/Rakocy feed-rate-ratio design method.

Grow bed area needed2.50 m²

How to measure your inputs

  • Daily feed rate: total grams of fish feed you add per day across your whole stock, typically 1-3% of total fish body weight.

Methodology

UVI feed-rate-ratio method (James Rakocy): grow bed area (m²) = daily feed (g) ÷ feed rate ratio (g/m²/day). Deep-water-culture systems run 60-100 g/m²/day; media-bed systems run 15-40 g/m²/day, since media beds host additional nitrifying bacteria capacity.

The feed-rate-ratio method: sizing by input, not by guesswork

Why feed rate, not fish count, is the right sizing input

Two fish of very different sizes eat very different amounts and produce very different amounts of waste — feed rate is a direct proxy for both nutrient output (what the plants need) and waste load (what the system needs to process), which is why the UVI method developed by James Rakocy sizes grow beds against feed rate rather than a simple fish headcount.

Why deep water culture and media beds need different ratios

Media beds host some nitrifying bacteria capacity directly in the media itself, in addition to whatever biofiltration exists elsewhere in the system — so they can process a given feed rate with less grow-bed area than a raft/DWC system, which relies more heavily on the water column and any separate biofilter.

Where this fits in a full system design

This answers one piece of aquaponics sizing — grow bed area for your fish load. Combine it with the Fish Stocking Density calculator (how much fish biomass your tank safely supports) to size a complete system from tank, to fish load, to grow bed, in that order.

Frequently asked questions

What is the UVI feed-rate-ratio method?

A published aquaponics sizing method developed by James Rakocy at the University of the Virgin Islands, which sizes grow bed area against daily fish feed rate (grams of feed per square metre of growing area per day) rather than fish count alone — documented in "Ten Guidelines for Aquaponic Systems."

How much should I feed my fish per day?

Typically 1-3% of total fish body weight per day, adjusted for species, water temperature, and growth stage — check your specific feed product’s guidance and your fish species’ requirements.

Why is the ratio different for deep water culture vs. media beds?

Media beds provide additional biofiltration surface area within the media itself, on top of whatever the plants and any separate biofilter handle — so they can support a higher feed rate per square metre than a raft/DWC system relying more on the water column alone.

Does this work for any fish species?

The ratio was developed and validated using tilapia on a standard 32%-protein commercial diet — it’s widely used as a general aquaponics design starting point for other species too, but a species with meaningfully different feed conversion or waste output could shift the real ratio somewhat.