Aahnay, it's the Tetra Whisper 3i, isn't it? Do you have a replacement cartridge? If you do, just switch cartridges. Otherwise, take it out and rinse it in some tank water. Then put it back in. Add some extra Prime and turn it back on. Keep an eye on him for signs of distress.
With my asthma, its odd what perfumes or smells will set it off. Ive been fine then had some one walk up next to me and instantly at the first breath started choking. I got a nice shirt on ebay and that happened when i opened the package, it was so horrible I through it in the truck bed.. stupid lady, not washing it, and she said she prides her sales!
Yeah, with any filter, if you suspect the bacteria has died then don't turn it on. That disperses dead bacteria into the water which then decay and cause ammonia. And because the bacteria that eats the ammonia is dead, that ammonia just sits in the water instead of being turned into nitrite/nitrate. Instead, change cartridges, rinse everything in tank water, and start over. Be prepared to do a mini-cycle and watch for ammonia spikes for the next week or so.