waterdrop
Enthusiastic "Re-Beginner"
I believe that very experienced aquarists, once they are quite familiar with how common ammonia and nitrite problems are, usually take action by performing a very large water change immediately upon suspecting either of or both of these might be the problem. About 20 min later they test for both poisons and if the level of either is above 0.25ppm, they perform another water change one hour after the first one and repeat until the goal is met.