Reply To: water changes
Even established tanks can show ammonia if there is a relatively sudden spike in production (several new fish or pile of uneaten food or dead fish), while the bacteria colony grows to accommodate the load, but I’d agree with looking to the tap water first. Depending on the type of water conditioner you use, you may be generating ammonia if your tap has chloramines, and if your conditioner only breaks apart the chlorine from the ammonia, rather than sequestering them. Also not as uncommon as we’d like for tap water to have trace amounts of ammonia in it.
edit: btw, my city tap water comes out at somewhere between 0 and 0.25ppm ammonia (I suspect chloramines).