Degassers (CO₂ strippers) remove carbon dioxide and can simultaneously increase air-side oxygen uptake. Common designs are cascades, packed columns and other air/water contactors where water is broken into films and droplets while air flows counter- or co-currently.
In RAS, fish continuously produce CO₂. High levels reduce growth and welfare long before DO becomes critical. Degassing is therefore often as important as pure oxygen dosing.
What a good degasser provides
- CO₂ stripping to air.
- Increased DO from air (cheap “free” oxygen uptake).
- Lower nitrogen-gas risk when design is sound.
- Basis for the strategy: air first, pure O₂ as additive.
Design notes
- Air flow, packing height and water loading (m³/m²·h) govern performance.
- Too little air → residual CO₂; too much water per area → short contact time.
- Trickling filters can combine nitrification and stripping — see trickling.
- Place stripping logically in the loop (after fish / before return) depending on hydraulics.
See also