What's Wrong With It?

[Giggity]

My three spotted Gourami has been fine for two months but all of a sudden, he just stopped swimming... He sits on the rocks in the back of the tank and doesnt move... every once and a while he'll eat a flake of food but not very often... i've had my tank for two months and have had him and another Gourami since i started the tank... hes my favorite little fishy and i don wanna lose him.... ill try to put a video of it on youtube but i dont know if i can... if i go near the tank hell dart in a circle but go straight back to where he was and not move again.... please help me....

 

[WILDER]

Need more info on.
Size of tank in gallons or litres.
How many fish and which type.
Water stats in ammonia, nitrite, nitrate, and ph.

Darting can mean bad water quality, toxins in the water, overdose of meds, stray voltage, parasites, ph shock, a fish is dying.
Swimming fast in circles can be swim bladder brain damage to internal parasites, the fish is dying.
Any signs of flicking and rubbing.
Does the fish look bloated or thin.
Does the fish look pale or darker in colour.