So I've had a lemon head oranda goldfish for about two months now in my cycled 43 gallon tank who had seemed to be thriving until about three days ago. My goldfish has been leaning towards one side and sometimes completely laid on that side. However, his leaning has not slowed him down a bit. He is still eating regularly, (sinking pellets and more recently freeze dried bloodworms), using the restroom regularly, (however there are what seems to be air bubbles in his feces), and easily making his way around the entirety of the tank. My water quality is this: ammonia and nitrites are 0, nitrates 15, and pH 6.9. I've done some research and I'm thinking it may be a swim bladder disease or I've been suggested it may have something to do with the angle of the tank light? I don't believe it to be any sort of problem with his wen being too heavy as he also likes to swim completely vertical, wen up. I hate seeing my poor guy like this. Should I try this 48 hour no food and then shelled peas method? Or should I try turning off the light for a few days? Any and all advice is welcomed! Thanks!