I have one small goldfish in a bowl, he is usually quite perky, blows alot of bubbles, and has a good appetite. I've noticed a bent in his tail for the past few weeks, i tryed giving him orange for vit c which he seemed to like.
Then i had to go away for 10 days, so i had to give him holiday pellets. When i returned, they had made the water very murky and Bruce (the goldfish) wasn't looking to pleased. But when i changed the water he looked alot better. Though after a day i noticed his tail seems to look more swollen at the end, and his top fins seem more closed than usual. He has also been sitting still at the bottom of the tank alot, when he always used to sit at the top. When he swims around, if he stops flapping, he seems to sink. I looked up some possible diagnoses on the internet and found it could be constipation, or sbd. I read that frozen peas could help, which i tried this morning. He went for them, but then shortly spat them all back up again.
I'm very worried because he is very dear to me!
I went and bought some 'disease safe' which i've put in his bowl, so i'm waiting to see if this has an effect. I've also got him some spinach and lettuce to see if he'll eat that.

Can any one offer any advice on what could help? Or what might be wrong with him?

Hi and welcome to the site.

Peas aren't going to help him now, I can tell you from experience he is suffereing due to poor water quality.
GF can't live in bowls. They need at least 10 gals of water per fish. THey produce alot of waste that makes the water toxic to live in. Hince they need a functioning tank with a filter and such.

So the first thing you need to do is a 100% water change. make sure the temps match so you don't shock him. Then you will have to upgrade to at least a 10 gal tank.
If you have more than one fish or a common or comet that will require more.

Sorry to say if you don't he won't make it long.

Thank you very much for your help.

It's just he's only 5cm long or so, and he looks lost in his huge (already upgraded) bowl as it is!
Theres no way i have room for or can afford a 10 gal, my landlord wouldn't be pleased!

But i will certainly do a 100% water change and hope for the best! I think the water must have became 'toxic' whilst i was away, though i have already done a water change.

Thanks again.

I know it seems over kill when the fish is so small, but it isn't.

If you look around the site here you will learn why, but in a "quick short response" this is why.

As I said before they produce tons of waste, as soon as you change the water they are mucking it up again.
When this happens they will produce a hormone that prohibits grow so as to try and adapt to their environment. This leads to a deformed fish and stunting.
GF can get as long as 12+ inches! When they aren't in the proper environment the stunting occurs and the fish's health starts to decline. It's life span is dramatically shortened and won't be healthy.

Now that said, the shape of bowls are bad too. They have let sounds and vibrations bounce off the sides, so everything is dramatically loud or like an earthquake to the fish. This causes stress which leads to disease.

If you can't afford a 10 gal tank you can substitute with a rubber maid container. It isn't as attractive as a tank, but it will work.
I will be honest again, even changing the water daily the fish will only live a very short time, they just can't adapt to that life. Sorry.

And actually, bowls really worry goldfish and stress them out because of the, well roundness. It reflects light ect ect and upsets most goldfish. Also to remind you, your fish, if it's growth isn't stunted, will grow. And it will grow to be quite large if it's healthy! And Ten gallons sounds like its huge but it really isnt. Maybe try checking out you're local petstore and seeing how big a ten gallon tank is before getting rid of that idea. Hope this helps.