What is happening in a fish tank if amonia is building up

There are two things that occur in aquarium ammonia chemisty. 1. the build up of natural ammonia and nitrate in the water. 2. displacement of oxygen in the water caused by the ammonia. This is a very real threat especially when you have a new tank that is still cycling or when the biological filter has been upset or removed.

Look for these main symptoms if you suspect ammonia poisoning in your fish tank:
-loss of appetite
-lethargic fish
-fish gasping for air/breath at the top of the water
-fish laying at the bottom of the tank
-red/purple gills
-red streaking on the fish's body
- fins becoming torn and jagged
-scales on fish falling off or turning black

Sorry its not enough info