Changes in our Ammonia Measurement Protocols

At Fish Welfare Initiative, one of our core values is evidence-based decision-making. This extends to our farm program, the Alliance for Responsible Aquaculture (ARA), where our water quality ranges reflect the best available science.

After further reviewing the literature on ammonia, we are updating how we measure it. Up to now, our threshold was 0.5 mg/L total ammonia nitrogen (TAN). From now on, we will instead use 0.05 mg/L unionized ammonia (NH₃)—the form that is directly toxic to fishes. We believe this change will make our program more in line with the literature and better able to improve the lives of farmed fishes.

Ammonia: An Important Water Quality Parameter

Ammonia is one of the three main water quality parameters (the others being dissolved oxygen and pH) that we track in the Alliance for Responsible Aquaculture (ARA). Ammonia builds up in ponds when uneaten feed and fish waste break down. If levels rise too much, ammonia can become toxic to fishes.

Over the years, we have seen how unchecked ammonia can cause serious stress and, in the worst cases, mass mortalities. This is why ARA field staff visit farms every month to measure ammonia, along with other key parameters. By doing so, we often catch problems early, before they turn into emergencies.

Program Associates Sanjay (left) and Chandu (right) after collecting an ammonia sample (left bottle) from an ARA farm. This sample will then be analyzed at our lab to ensure that levels are appropriate for fish welfare.

Unionized Ammonia: A Better Indicator for Welfare

Ammonia comes in two main forms:

• NH₄⁺ (ionized ammonium): mostly harmless under typical farm conditions.

• NH₃ (unionized ammonia): highly toxic, able to pass through fish gills and directly damage their health.

  
  

Ammonia measurement devices commonly measure a separate form called total ammonia nitrogen (TAN), which includes both of the above forms. However, TAN can be misleading because it includes the toxic and non-toxic forms of ammonia, as these depend on temperature and pH (see figure below):

• At low pH and temperatures, TAN may look high, but NH₃ remains at safe levels.

• At high pH, TAN may appear moderate, but NH₃ can be dangerously high.

In conclusion, NH₃ is the relevant form for fish welfare because it shows when they are at real risk.

The proportion of toxic, unionized ammonia (NH₃) increases with pH and temperature. As a result, total ammonia (TAN) only gives a partial picture of ammonia toxicity for fishes in aquaculture.

What This Means For Our Farm Program

At the ARA, we initially measured total ammonia because that’s what most devices provide. There is also ongoing confusion in the academic community about which form to use, which contributed to our adopting TAN in the past.

Looking back at our past water quality data, we found that if we had used the NH₃ standard all along, we would have recorded about 3.5 times more ammonia problems. This means that until now, we were likely underestimating the risks.

Switching from TAN to NH₃ means:

• More out-of-range detection: Ammonia problems may show up in ~3–6% of monthly tests, compared to the old ~1–2% rate.

  • This may affect our OKR 3.2, which tracks how often we detect poor water quality during farm visits.

• More fishes helped: Identifying more problems means more opportunities to improve water quality and fish welfare.

  • This may affect our OKR 3.1, which measures fishes helped per dollar spent.

    
    

We have considered adjusting our goals upwards because we expect an increase in impact due to this adjusted range (rather than programmatic change). We ultimately decided not to immediately change goals and instead track both TAN and NH₃ throughout a transition period. We plan to reevaluate this decision in 2–3 months and will share an update.

This adjustment is a small but important step for our program. It shows how sometimes details—like the exact form of ammonia—can make a big difference in our ability to improve the lives of these animals.

You can find our full decision-making process and supporting literature in this document.