04/02/2025
Let's talk about nitrate in recirculating aquaculture systems (RAS).
It has been widely accepted that, while even low concentrations of nitrite and ammonia are harmful and, indeed, deadly for fish, only very high concentrations of nitrate affects fish health and welfare.
Research over the past 10-15 years has shown the latter to be a false assessment, yet somehow the belief remains in many circles. Even "hardy" fish like Clarias gariepinus (African catfish) have been shown to be negatively affected by very moderate nitrate levels, experiencing loss of appetite and highly elevated plasma cortisol levels (see for example Schram et al 2012). Fish which are more sensitive to water quality are even more grossly affected. Moderate levels of nitrate (80-100mg/L) had "chronic health and welfare impacts" in rainbow trout (Davidson et al, 2014) and cause "abnormal swimming behaviour and increased incidence of deformities" (Davidson et al, 2011).
Despite the fact that this research is already nearing 15 years old, nitrate is, in many cases, still not monitored on a regular basis. At Saga Aqua we were first in Scandinavia to have equipment to monitor nitrite and nitrate levels constantly and in real time. In fact, when we discovered this equipment at Aquamonitrix® - On-line Analysers, we immediately contacted them, flew to Ireland and became the distributor for Scandinavia. We saw this equipment as a vital component for RAS and one which would allow us to optimize water quality with respect to nitrite and nitrate, and further secure optimal fish health and welfare conditions.
When we set-up your system using this equipment, we can follow the development and establishment of the microorganisms via nitrite and nitrate so that you can be assured that your biofilter is functioning as it should. In the event that we install a denitrification filter in your system, we can also follow it's development and show you graphically where your nitrate levels are in the system before, during and after feeding events so that you can feel assured that your fish are in an environment without stress due to poor water quality. Should you choose not install a denitrification filter, we can provide the same service where we can optimise your water exchange rate to keep nitrate levels at a safe level for your fish. 🥰
Just give us a call and let us demonstrate how Saga Aqua's system design prioritises fish health and welfare. hashtag hashtag
