Oxygen (O₂) is the #1 critical water quality parameter in Recirculating Aquaculture Systems (RAS). Without proper oxygen levels, fish stress, stop eating, and can die rapidly—even if all other water parameters (ammonia, nitrite, etc.) are perfect.
Oxygen is Vital in RAS
1. Fish Survival & Growth
Fish require 5–6 mg/L dissolved oxygen (DO) for normal activity.
Below 3 mg/L, most fish gasp at the surface, stop feeding, and suffocate.
Optimal DO (6–8 mg/L) boosts growth rates and feed conversion efficiency.
2. Beneficial Bacteria Depend on O₂
Nitrifying bacteria in biofilters need O₂ to convert toxic ammonia → nitrite → nitrate.
Low O₂ crashes biofiltration, leading to ammonia spikes.
3. Prevents Stress & Disease
Hypoxia (low O₂) weakens fish immunity, increasing susceptibility to bacterial infections (e.g., Aeromonas).
Maintain Optimal Oxygen in RAS
1. Aeration Methods
Method | Best For | Pros |
Air Stones/Diffusers | Small RAS | Cheap, easy to install |
Venturi Injectors | Medium RAS | High O₂ transfer, no moving parts |
Pure Oxygen (O₂) Systems | Large/commercial RAS | Extremely high DO (10+ mg/L) |
Surface Agitation (Paddles/Spray Bars) | Backup aeration | Simple |
2. Monitoring & Automation
DO Sensors (optical probes are most accurate) with alarms for low O₂.
Automatic Oxygen Regulators (for pure O₂ systems) to prevent overdosing.
3. Emergency Preparedness
Backup Battery Air Pumps (for power outages).
Oxygen Cylinders (for critical systems).