Can a fish go blind? My yellow tang is acting really really weird. She is the only fish with a problem. She is swimming real slow with her head facing up. If she bumps into a rock or the glass she freaks out. Plus she's not to have much strength. When she gets near the return or powerhead it just pushes her back. The system is a 125 gallon with a lieutenant tang, two clowns, brusa trigger, and a Puffer. She has no damage to her fins. But does not seem to want to eat. The tank is a FOWLR and has nitrates. She is about 6". I don't think it would be good to move her to the reef tank because that tank is only 3' long. What should I do?