Strange clownfish problem

[SmallFry]

On Friday night I noticed that my Tomato Clown was behaving oddly, seemed to stay at the top of the tank with his back out of the water, breathing heavily. Also seems to be blind and bumps into stuff. I could even touch him which is unheard of - usually he tries to take a chunk out of me.. Eyes are totally clear, no white spots discharges or fuzziness - looks like the picture of health apart from the odd behaviour. The other fish, a Kole tang and a Coral Beauty acquired a week ago are just fine as far as I can tell.

Saturday morning he seemed worse , sometimes on his side. At that point he still could swim normally if he decided to. Still breathing heavily and still not eating; I even put some Mysis right in front of him with a turkey baster but he wasn't interested which is out of character. I hauled the invertebrates out of the tank and moved them to the big tank downstairs. I then dosed the tank with Paraguard because without any real clues as to what is wrong it seemed worth a try.

Tonight he's much worse. He's just floating around on his side or upside down, occasionally wedging himself above a powerhead or in a rock. He's still not eating, nor has any signs of anything wrong other than the obvious floating around upside down. All other fish are still fine. I tried a 10 min freshwater dip as a last ditch effort since I don't have any better ideas and thought it might be something like a parasite in his gills causing the heavy breathing.

Has anyone experienced anything like this or know what it is? I know there's been a lot of upheaval in the tank due to the fact that I've been using it as a sort of quarantine for new fish coming in for the new 75 gallon. Most of the upheaval has been in rearranging rock work to try and control his aggression. I also imagine he found suddenly coming up against a Kole Tang that wouldn't be bullied quite stressful too.

I realise this is less than ideal practice, but I can only run two tanks, and due to aggression issues I have decided that the clown would be the last or one of the last into the tank. While this has it's risks it seemed better than the alternative..

Temp 26C
pH 7.8 (normal for that tank)
Nitrate 5ppm
Ammonia 0
S.G. 1.023

So in the time it's taken me to write this he's lost the struggle - I guess the question now is was it stress or something contagious or transmissible? Hopefully not the latter for the sake of the other two fish, whom are still OK. I suppose this shows the importance of quarantine - at least the other fish in the 75 are safe even if it is contagious..

Kind of bummed to loose my first ever saltwater fish even if he was a miserable piece of work...