AAAAH! I don't think I have seen water that dirty EVER. EVER.
Even supposing you don't give a living crap about fish how on earth your you stand the sight of that thing on your desk, let alone the smell?!
See if this person had not a betta but a filty mousecage on his desk smeared with faeces everyone would be too mad to speak. But since its a fish, people either don't know they can feel pain or don't care >:(
Normally I advise against this but I TOTALLLY vote you abduct him. People will find it FAR harder to believe you abducted him than that he finally succumbed to that filthy water.
THAT JUST ISN'T RIGHT.