I have had two goldfish since the beginning of december and everything seemed to be fine until about three weeks ago - the smaller of the two was starting to swell up (he had slight swelling from inception) and appeared to be lethargic!  However, last Wednesday evening I went to feed them and he was upside down at the top of the tank gasping for air!  I got a shock called the vet and he said it was possibly swim bladder issue - to starve him for a few days and then add some shelled peas and go to the pet shop and see if they could help!
I starved the fish in a separation tank - his trail became clear and he now has no trail - so I thought he could have been constipated and thus caused the problem.  Spoke to the pet shop and they gave me some solution to put in the water to help - Revitaliser Tonic this seems to have made him more perky so I put him in with the other fish for about an hour and a half the day before yesterday and found him at the bottom of the tank upside down - I was trying to get him to eat the bugs that the pet shop also gave for me to feed to him over the weekend!  The other fish taught him to eat them (most of them anyway).
The fish is looking brighter and more active but he is still swollen and swimming sometimes upside down in his tank - has anyone got any advice.  Thanks.

Water is reasonable quality - I have him in a hospital tank - will try the peas and see how that goes.  Thanks.

Thanks for that will have to get some salts - as do not have any in at the moment - will keep you all updated - strange how a little fish can cause you such worry - I have become quite attached to them - they are looking at each other (if that is possible) through their respective tanks at the moment - how sad is that!!  I would just like to seem them back together full of the joie de vie!! 

Aww... that's sad ): At least you did your best!