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PUREFLOW BIO / ENGINEERING FIELD GUIDE

Feed Conversion Ratio and Waste LoadWhy Feed Sets Your Filter Size

How FCR links feed to growth and waste, and why daily feed is the best starting point for sizing filters and oxygen supply.

Explore the process ↗Open the workbench
6 MIN GUIDEUPDATED NOVEMBER 2026
Concept illustration of culture tanks connected to a complete RAS water-treatment train.SYSTEM CONCEPT
AI-generated educational concept illustration; not a Pureflow installation photograph or an approved construction drawing.
01Understand the mechanismInspect the relevant process stages.
02Review the operating dutyKeep assumptions and measured values visible.
03Prepare the next decisionUse the guide, tools and project checks.
INTERACTIVE PROCESS ATLAS

See the mechanism.
Understand the duty.

Select a route or a stage to inspect the process. The cutaway explains the equipment and water environment; it is a teaching illustration, not a project drawing.

Swipe horizontally to inspect the equipment. Stage buttons below also centre the selected component.
Inside a recirculating aquaculture treatment systemA cutaway culture tank connects to a rotary drum screen, moving bed biofilter, degassing tower, sump and pump, oxygen cone and enclosed UV reactor. Blue arrows follow recirculating water. An amber line takes drum-filter waste out of the loop. Equipment shapes and motion explain the process; dimensions and timing are illustrative.SEPARATE WASTE ROUTE VENTILATED OFF-GASCONTROLLED O₂ SUPPLY01 CULTURE TANK02 DRUM SCREEN03 MOVING BED04 DEGASSING05 SUMP + PUMP06 OXYGENATION07 UV TREATMENTTAN-NNH₄⁺ → NO₂⁻ → NO₃⁻PUREFLOW / INTERACTIVE PROCESS ATLASCONCEPT LAYOUT · NOT TO SCALE
Follow culture water through the coordinated treatment train and back to the stock.
Selected process stage

Culture tanks

Collect waste before it settles.

How it works

The culture tank is both an animal environment and a hydraulic vessel. The return flow should distribute oxygenated water and move settleable waste toward the intended outlet. Tank shape, drain arrangement and the behaviour of the stock determine how well this happens.

What to establish
  • Confirm the operating water volume and peak feed.
  • Check circulation, drain capture and access for inspection.
  • Record oxygen at the animal zone, not only in the return pipe.

Read about biomass and loading ↗

Filtration mode. Wash sequence and timing are illustrative. Geometry, stage order, pipe routes and equipment configuration are conceptual. Use the approved project design, operating instructions and verified model data.

Key takeaways

  • What FCR is: Feed conversion ratio is the weight of feed you use per kilogram of weight the fish gain.
  • Feed becomes waste: Fish keep only part of what they eat.
  • Using it for design: Estimate peak daily feed, then size the drum filter, the biofilter and oxygen supply for that load, with margin.
  • Improving FCR: Feed the right size of pellet, avoid overfeeding, keep water quality good so fish eat well, and record feed and growth every week.
Reference illustration for Feed Conversion Ratio and Waste Load: Why Feed Sets Your Filter Size
Equipment reference visual; not evidence of a completed installation.
THE SHORT ANSWER

What fcr is

Feed conversion ratio is the weight of feed you use per kilogram of weight the fish gain. A lower number means less feed is wasted for the same growth.

Feed Conversion Ratio and Waste Load - Pureflow Bio
Reference visual. Equipment configuration and project details must be confirmed separately.
AQUACULTURE & RAS

Feed becomes waste

Fish keep only part of what they eat. The rest leaves as solids and dissolved nitrogen, which becomes ammonia. More feed means a bigger load for the drum filter, biofilter and oxygen supply.

PLANNING WORKBENCH

Work with your own numbers.

Use the tools below to explore the relevant arithmetic. Enter measured values or declared assumptions. An estimate does not establish equipment capacity, biological performance or a safe operating limit.

Observed feed conversion ratio

Calculate a period FCR using recorded feed and net biomass gain over the same period.

Assumptions and limits

Use a consistent stock accounting method and include movements and mortality where appropriate. This is an observed ratio, not a growth forecast.

—Observed FCR · kg/kg
Enter your values, or load the labelled arithmetic example. No design values are pre-filled.
FormulaFCR = feed supplied ÷ net biomass gain.
Convert units before you calculate
Choose units and enter a value.

Planning arithmetic · inputs remain visible for review · example values are not operating recommendations

AQUACULTURE & RAS

Using it for design

Estimate peak daily feed, then size the drum filter, the biofilter and oxygen supply for that load, with margin.

AQUACULTURE & RAS

Improving fcr

Feed the right size of pellet, avoid overfeeding, keep water quality good so fish eat well, and record feed and growth every week.

Pureflow Bio equipment for this

All aquaculture equipment →Pumps, tanks, oxygen and filtration.Standard drum filters (RDF) →Automatic solids removal.MBBR biofilters →Moving bed biofilters.
PROJECT REVIEW

Review the design at peak load

Use these questions to prepare a project brief or an operating review. Check an item only when the information has been recorded for your installation.

0 of 3 checked

This checklist is a working aid in the current page session, not a saved maintenance record.

QUESTIONS

Feed Conversion Ratio and Waste Load FAQ

What is a good FCR?

It varies by species and feed. Compare it with figures from your own farm over time.

Does poor water quality raise FCR?

Yes. Stressed fish eat less efficiently.

KEEP READING
Biofilter sizing→Drum filter sizing→Stocking density→Aquaculture Filtration Systems: Mechanical, Biological and Disinfection ↗Biofloc vs RAS vs Earthen Pond: Which System for Your Farm? ↗

Discuss your system with Pureflow.

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