my 18 year old fish is very ill

Question
QUESTION: Hi there, could you please offer me advise?
I have an 18 year old goldfish who until recently has been very happy and healthy. 5 days ago he started acting strange and seemed unable to swim. This got worse very quickly to the point were he is now spending all his time lying on his side at the bottom of the tank. He is unable to upright himself for any length of time and if he does manage to swim he sinks rapidly back to the bottom (very distressing to watch). I've done a partial water change, added stress treatment and a de-chlorinator treatment as usual and changed the filter. I believed he was just dying of old age so i left him for a day, thinking that he would just pass away but no he didn't. After reading up on his behaviour and visiting pet stores i now believe he has swim bladder? I have added aquarium salt to the water with no improvement and have resorted to hand feeding him as advised as otherwise he cant feed. He continues to feed very enthusiastically from feed held between my fingers. One of his eyes has rubbed against the stones that he lying on so doesn't look to nice but he can definitely still see.
I've read that it may be constipation so have purchased some peas to try.  

How long would it take for the salt water help him? Should i continue to feed him? Should i treat with an antibiotic such as quinine sulphate or TPM sulpha? Various sites states poor results for treatment of swim bladder but if i continue to treat/feed him, who much longer would he live?
I don't want to prolong his life if he is unable to swim or feed himself. I'm finding it very distressing looking at him as ive had him so long.
I was looking at various ways to euthanise him if no improvement is made? Some sites recommended the anaesthetic Finquel, MS-222. Where could i source this? What would you recommend?

I would be grateful for any advise as im finding the whole situation distressing.

Thanks in advance  joanne

ANSWER: Well Joanne, i think you ought to give yourself a pat on the back for keeping your goldfish alive for 18 years! Unfortunately swim bladder is quite common in older fish and some treatments can work for other while some may not. If you have caught this disease fast enough then you might be able to help him. As for the MS-222 i would look around aquarium shops, pet stores, go and ask your local veterinarian, you could also try to find it in your local nursery. You are doing the right thing feeding him although if you think he might be getting better try to teach him how to eat by himself, as he will think that you are going to feed him forever. Thats all the advise i can give you at the moment, Good Luck i hope all goes well.

---------- FOLLOW-UP ----------

QUESTION: Hi again, sorry to bother you again but ive now tried peas with him and unfortunately no improvement. Should i continue with this treatment? If so, do you know how long it would take to work? Should i try an anti bacterial agent in the water or do you think its just old age? How long should i let him be like this? Do fish with swim bladder disease have any quality of life or is it kindest to euthanise him?

Thanks again for your advise
joanne

Answer
Unfortunately Joanne, with a fish that old it is hard to tell if you can fix it. I personally haven't had much experience with swim bladder as the fish a first examined had died quite soon after me meeting him. There is no harm in continuing your treatment (that you are doing exceptionally well) But i don't know how long he might last for, given his age. Also it wouldn't hurt to try anti bacterial agents and other medications, but be prepared of it having a chance of not working. I think that its up to you to put him to sleep. Its a horrible thing to think of but i would continuing what you are doing for another week or so and then if there is no improvements get back to me, i will try to find out more about the disease to hopefully help you and your sick fish. Good Luck Joanne, hope to hear from you soon.