Poor guy didn't make it through the day. I got up to get ready for work and found him upside down, no gill movement, and unresponsive. Not surprising considering how bad he looked when I went to bed, I'd have guessed ammonia burns from the look of his whiskers, fins, and skin but I tested ammonia and nitrites three times, once immediately post bio-filtration, once immediately before bio from a skimming drain, and once from deep in the tank, and found zero in all three locations. Again all the other cats in the tank are acting fine and showing no signs of illness or injury.