Can anyone help? One of our goldfish(comet) is poorly. We thought he had swim bladder and tried the peas advice but he is no better and now we think he has gone blind. He does loop the loops when we put the tank light off at night and at feeding time he seems unable to see the food although he does seem to sense it and heads in the general direction. He looks to have a bit of a bend in his body, but not all the time. He also lies at the bottom a lot.

I agree with Nicole.
And I'd like to add, that the fish probably isn't blind, unless you see a miscoloration in the pupil when it reflects light. You should see a strange blue kind of cloudiness in it, if the fish is turning blind.