I think my goldfish is dying :(

Question
I have a black goldfish that has started to turn an orangey colour and is floating on his side and not eating. He is in a 3L bowl and i recently changed the water. When i change the water i make sure that i ease him into the fresh water from a container that contains the old water so that the change in temperature isnt a shock. I also use 4 drops of ammonia detoxifier and 12 drops of biological filtration booster. Is this wrong? is my bowl too small? Is it too late to do anything to fix this?
Thanks

Answer
Yes, your bowl is too small. A goldfish should be in a 20 gallon tank. They are simply too large bodied and create too much waste to ever live out their lives in a bowl. Goldfish are very long lived and should live around 20 years. In a bowl you might get a max of one or two years, and he will never reach adulthood before he is killed prematurely from constant stress.
Get him a much larger tank, start doing regular water changes and don't use "ammonia detoxifiers", they don't really work and they don't make it so you don't have to do water changes.
The best thing for you would be an under gravel filter. It is biological filtration that will aerate your water really well, and get a lot of beneficial bacteria growing that will eat the ammonia and nitrites leaving you only with nitrates that are much less toxic. You will still have to do water changes of course, but not as often. Get a water testing kit so you can see what your water levels are at - Ammonia and Nitrites should ideally be at 0, Nitrates will be removed with water changes (along with ammonia and nitrites until you get enough bacteria) and should never go above 20.
Also, always keep the new water the same temperature as his old water, no matter how slowly you put him in it will shock his system. And they don't need very warm water, 70 degrees is just fine.