Water Quality
Managing Nitrite in a New RAS Hatchery
A field note on Jentan’s early nitrite challenge, the temporary protective role of salt and why biological filtration remains the long-term control mechanism.
By Jentan Hatchery Team · Published · Updated · 1 min read
- Location
- Ozubulu, Anambra State, Nigeria
- Species
- Catfish
- Fish stage
- Fry / fingerling
- System
- RAS
- Problem
- High nitrite
- Equipment
- Biofilters, circulation pumps, aeration and water-testing equipment
- Outcome
- Nitrite reduced while the team continued to focus on biofilter stability and operating discipline.
Recorded readings
Nitrite approximately 0.2 mg/L initially; approximately 0.02 mg/L after intervention and continued monitoring. Nitrate approximately 5 mg/L during the early period.
The problem
During early operation, nitrite was measured at about 0.2 mg/L. In a new recirculating system, this is a warning that the biological filtration process may not yet be fully mature or that loading is temporarily exceeding the system’s conversion capacity.
What we did
Salt was used as a short-term protective measure while the system was monitored. Subsequent nitrite readings fell to about 0.02 mg/L. The important distinction is that chloride can reduce nitrite uptake by fish, but salt does not replace a functioning nitrifying biofilter.
Operational lesson
- Test nitrite routinely during start-up and after major stocking or feeding changes.
- Treat salt as protection, not as the biological solution.
- Maintain aeration and circulation through the biofilter.
- Avoid sudden increases in feed load while the biofilter is stabilising.
- Track ammonia, nitrite, nitrate, pH and alkalinity together rather than in isolation.
Caution
Water-treatment decisions should be based on measured values, fish behaviour and system context. Different farms have different source water, biomass, temperatures and biofilter maturity, so a treatment used at one farm should not be copied blindly to another.
About Jentan Hatchery Team
Water Quality & RAS Operations
Field notes from the Jentan Fish Hatchery & Farms operations team in Ozubulu, Anambra State.