ALL fish give off some ammonia. It's what you get after they digest protein from their food, so it's always present in their wastes. It also forms whenever a fish, plant, or any living thing in your tank dies and decomposes.

Why it's bad is because it interferes with the ability of your fish to use oxygen from the water - that's why one of the symptoms is that the fish go to the top of the water and gasp for air, even if you have a good filter in the tank. It also causes damage to the gills and fins, causing them to split. It can also cause what's equivalent to a chemical burn on their skin, and black patches can appear on the fins or body.

The good news is, as long as you keep your goldfish in a large enough tank, only do partial water changes (never clean out the whole tank & gravel), and don't overstock or overfeed, in a few months, there will be bacteria in the tank that use the ammonia as their source of energy, and they'll remove the ammonia for you by converting it to nitrite (also toxic to fish) then to nitrate, which is safer. It can still be a problem if you let it build up too much, which is why regular (weekly) water changes of 25% are suggested.


NOTE: If you ever use an antibiotic to treat a bacterial disease, the anitbiotic will kill the "good" bacteria as well, so expect there to be ammonia again while your tank undergoes another cycle.

It kills fish. It's what is in their waste, and can build up in the water and cause actual burns to start on their bodies. It's highly acidic, and found in human urine. If a human or animal urinates on dark cloth, the amonia in the urine is so corrosive that it will bleach like clorox. Amonia is what kill grass and plants when a dog urinates on them. Knowing that it bleaches, kills plants etc,,,,,,,you can understand why it would be deadly to fish when it builds up a large amount in their water.

before I read the abouve paragraph, I changed all the water and the gravel! Now I am afraid that there is not enough ammonia eating bacteria!! Now what!?

i have had 2 gold fish for nearly 2 years added 2 more fish then filter broke down got a new one  3 weeks later they died they had like a white skin on top of their own to you think they died of a ammonia posion.