My male O. Clown (Bert) seems to have a white-ish semi-clear film on his back. Hard to see if the light isn't just right. He is tank-bred and I have had him for about 18 months and has always been very healthy, happy and active. Shares a 55-gal with Notch (female O. Clown), also tank-bred, but I've had her for almost 2 years. He doesn't seem stressed or exhibit any abnormal behavior. I first noticed this film about 5 weeks ago. I searched but didn't find any answers, so I shot a photo (not easy with an active clown!) to post here. Help?