My Sick Goldfish

Question
My 3year old Goldfish is seriously ill.Over a period of 2days he has loss of appetite,all fin bases appear badly bruised (scarlet in color),it is almost like he is shedding his entire skin from head to tail. it just seems to be peeling off.Can you please help me to eradicate his illness and find a remedy.Thank you.

Answer
Hi Shaz,
It's hard to tell exactly why is he is sick without all the details. For example, it would be much easier to know if you were to let us know the size of the tank, how much and how often you feed him, what other fish if any is in with him, what temperature do you keep the water at, etc.
Without this info, I'll try to help you the best I can. Most likely he is under constant stress due to chemicals in the water from poor water quality. Do you test weekly for ammonia/nitrate levels? If his ammonia or nitrates/nitrites levels have been high for too long, it will kill him. You need to do more water changes, and the smaller his tank is, the more water changes you need to do.
The reason is that ammonia is invisible, and though your tank may look clean, he could be suffering from a deadly toxin. The only way to truly get rid of ammonia is to change out the water. I would say - if you have a 20-30 gallon tank, then do at least 25 weekly. If you have a ten gallon, 25 twice a week, and anything smaller you'll need to do one at least every other day.
Goldfish process their food twice as fast as most other fish, and this means they poop more, and therefore produce a lot more ammonia much more quickly. In a small tank and in any bowl it will fill up with ammonia much too fast and eventually kill him.
He may have seemed fine for the longest time, but it is hard to tell how a fish is feeling. They can't exactly scream for help! (though sometimes it looks like it...)
If you have him in anything under a 20 gallon, especially without a filter, then please consider upgrading to a larger tank and adding a high quality filter.
Most fancies grow to be 6 inches by their third year, and if he is much smaller than this than you are stunting his growth and considerably reducing his life span. (Goldfish can live up to 20 years.) Comets grow even larger (up to a foot) and will need an even bigger tank.
However, if you do have a larger tank, and your water quality is good, you have a high quality filter, than it seems he is under a lot of stress for whatever reason (maybe due to another fish) and you should add aquarium salt to help reduce his stress. If it continues try adding a sort of natural remedy all (like what they have for bettas) and hope that helps.
Hope this helped you, best of wishes to your fishes.