RAS systems
basic RAS calculation: volume, density, biofiltration, aeration — when it pays off
RAS systems
What it is:
Recirculating aquaculture system: tanks + mechanical filtration + biofilter + aeration — year-round fish regardless of weather.
Density:
30–80 kg/m³ depending on species and system — vs 0.5–2 kg/m³ in a pond.
Biofilter:
The heart of RAS: nitrifying bacteria convert ammonia → nitrates; size 5–15% of system volume.
Throughput:
Pump cycles the volume 1–2 times/hour; sludge separator removes solids.
Economics:
Capex $50–150 per kg of yearly output; opex: feed (FCR 1.1–1.4), electricity, oxygen.
Species:
Sturgeon, trout, tilapia, clarias — high price and density; carp is marginal.
When it pays:
High fish prices, water/land scarcity, year-round sales — else a pond is cheaper.
Start:
Pilot 5–10 m³ on tilapia/sturgeon; don't scale without half a year of operation.