Just to add to what others are saying about the water. An other way of understanding what we are saying - the water might be the most pure in the world, but what happens to the water after its been left for a while. It gets polluted its like if you pooped in a bowl you would see what is going on, but on a more concentrated level. Does that help?
Again to think of it an other way - your tank will be full of water that has a massive amount of ammonia in it which is kind of like putting you in a glass box full of carbon monoxide it will kill you as the ammonia will kill your fish. How you have kept fish alive in there for 2-3 years is beyond me and I really do think you are incredibly lucky.
No fish can get rid of the chemicals in the water, no fish eats poo all that happens is they swim past/over it and the current breaks it up and it falls through the gravel.
How often do you do water change? Do you do water changes?
I still stand by my advice of getting rid of your current fish and starting again.
Again to think of it an other way - your tank will be full of water that has a massive amount of ammonia in it which is kind of like putting you in a glass box full of carbon monoxide it will kill you as the ammonia will kill your fish. How you have kept fish alive in there for 2-3 years is beyond me and I really do think you are incredibly lucky.
No fish can get rid of the chemicals in the water, no fish eats poo all that happens is they swim past/over it and the current breaks it up and it falls through the gravel.
How often do you do water change? Do you do water changes?
I still stand by my advice of getting rid of your current fish and starting again.