why do I have ammonia NH3?

All aquarium livestock produces ammonia, how much build up depends on how many animals are kept and how much you feed versus how efficient your filters are. This is why it is so important to slowly introduce livestock over many months to your aquarium allowing avoiding new tank syndrome ; it allows the biological filter bacteria to breed that consume the harmful ammonia as it is produced.

We are often told that people with mature aquarium aquariums don't have ammonia. This is false all aquarium have ammonia being produced if they have live stock. They may not register ammonia as the filters are keeping up with its production, however sometime bacteria colonies can be affected and population’s crash, this can be caused by water parameter fluctuations or pollutants; when this happens the same rules apply here as to removing ammonia as a it does to new customers.  On ponds blocked filters are also a leading cause of NH3 issues.