I am really worried about my fish... :(
My Electric Yellow is swimming eratically (somersaults etc.) and has lost his appetite. He is disorientated also and misjudges objects bumps into ornimates and such, he seems almost half blind. I don't know what to do...
Can someone please give me advice?

Does he have any other signs? such as is he swollen, patches on body or fins, loss of color, rapid gill movement, scraping against things? Or is he just swimming wild? If he is just swimming wild check your ammonia levels.

no other signs of illness, ammonia was ok when I checked yesterday. 0 ammo reading from test. he is not flashing.

what size tank is he in, is this a new fish, what other fish are in there with him? have there been any sudden changes?

Coast Runner, to follow along on jdizine's line, if other fish in the tank are not harrassing him, then there is something about the water causing him problems, especially if the wierd behavior was sudden. The erratic swimming and bumping into objects points to some toxin in the water.

It is important to know, as jdizine asked, if the fish is experiencing breathing problems and how other fish, if any, are behaving. Was your fish behaving this way when the ammonia tested at 0? How long has he been behaving this way and did anything change just prior to the behavior beginning?

So..

Have you had anything on your hands or has there been anything in the air (vapors) that might have been introduced into the tank such as oils, perfumes, tobacco, etc.? Any new chemicals used?

What are the current pH, Ammonia, Nitrite and Nitrate test levels? Are they abnormally high?

Was a water change done very recently? If so, how much and was a declorinator used?

Have any new objects or fish been added to the tank? Poisonous fish?

Are there any objects in the tank that might be causing a problem? Metal, etc.

How long has the tank been established and how long has the fish lived in the tank?

That's it for now. Questions, questions, but the answers will help lead to a quick diagnosis and ultimate solution.

[Edit]:If possible, get the fish in a hospital tank or a bucket with an air stone, for starters. If the fish improves, the problem is in the main tank. You will have to make an 80% water change. Keep an eye on other fish. If there are more in the main tank, you will have to remove them as well, while changing out the water. We can talk about other related steps when we have more information.

Symptoms match an advanced parisitic issue in my opinion (have lost fish in the past with this myself). Specifically HEXAMITA is likely the culprit (the internal version of HITH that effects the gastrointestinal tract). I'd check for white stringy "wool like" excrement and if present treat with 'Metronidazole', allthough once the nervous erratic behaviour has started it can be hard to successfully treat unfortunately :(.

Would it have anything to do with the fluro over the tank? I've recently changed the colour from a standard white to a pinkish hue. The tank looks really nice.

if you could just let us know the answers to our Questions. it will help everyone out tremendously.

the answers to those questions would be very helpful is there anyway you could change the light back it is worth a try