Do not listen to anything you read.
Ammonia, NH3, is a gas. It is highly toxic to most forms of life, but not all. When ammonia is dissolved in water it breaks down into two components: Ammonia (NH3) and ammonium (NH4). Most of our hobby test kits, but not 100% of them, read what is called Total Ammonia (TA), This is the sum of NH3 + NH4.
What determines how much of an any TA reading is in each form depends upon two factors. The first, and most important, is the pH of the water while the second is temperature. As either of these two parameters rise, the amount of the TA that is in the NH3 form rises. Of course, the reverse also applies. As the pH drops under 7.0 the ammount of NH3 declines rapidly until, by about 6.0, the TA is basically 100% NH4.
Why is this information relevant to use in the hobby? It is because we need to protect our fish from the effects of NH3 and not so much NH4. The latter can still harm fish but it takes a higher level and a longer exposure for this. So, for those p[eople who still cycling with fish (ugh), the key to if and when you may need to protect against ammonia matters. Reducing ammonia when it is not needed or using chemicals to change the balance between NH3 and NH4 will slow the cycle. Most of the mircoorganisms that help us keep tanks safe from ammonia prefer to consume NH3. However, many can use NH4 if they must, but they do so less efficiently which means they do it more slowly.
Ideally, a cycled tank had 0 TA which means none in either form. However, during a cycle or an ammonia spurt in a a cycled tank, knowing what is the best thing to do really depends on how much of the TA is in the NH3 form. Before the digital age this required doing some complex math to get the answer, Today we have digital calculators which do this quickly.
One this site there is some information on ammonia and nitrite and how to deal with them both. I wrote two articles on rescuing a fish-in cycle gone wild for this forum. The second one explains the above in depth and explains how to deal with them. It includes a link to an online calculator for ammonia and ammonium levels.
https://www.fishforums.net/threads/rescuing-a-fish-in-cycle-gone-wild-part-il.433778/
In connection with the online calculator there is also information that should also help you. It is a very short and clear explanation of testing and the two different measurement scales available:
https://www.hamzasreef.com/Contents/Calculators/NitrogenIonConversion.php
Why is it important to know ammonia and nitrite levels when no fish are involved. At 5 ppm of TA or Nitrite measured on the Nitrogen scale used by science, will stall a cycle. But we tend to test using the Total Ion (TI) scale, so we need to convert those 5 ppm readings into the equivalent ones using the TI scale. For ammonia this is about 6.25 ppm and for Nitrite it is about 16.5 ppm. These are calculated using the thin info on the above link.
edited to correct spelling/typos
edited to correct a lot more typos misspekkings and missing words.
