why does NH3 go up when I do water changes?

 

Free ammonia NH3 can go up when you do water changes because the water you use for water changes has a higher pH.

 

NH3 and NH4 always form equilibrium with pH and temperature. When we do a water change (especially if you are a lazy fish keeper) the new water will often be harder and higher pH than the water you are removing. This is because organic acids from waste and biological activity will remove the waters hardness and lower the pH. The move to a higher pH will unlock NH4 into NH3 and the transition can happen in fractions of a second.

 

A seneye device will report this change in pH, temperature and free ammonia.