Funky smells usually mean something's up. Sometimes, you get a rainforest kinda scent goin on, but I can't imagine that scent would do much harm. Run some purigen in their rooms, it should strip the water of any organic funky stuff.
My little brother has asthma, it was worse when we were younger, but we were always out fishing and playing in the river. My brother, in fact, used to stock the bait shop with leaches. I can't recall any reaction from anything other than pollen when we were out.
Maybe they have a plant allergy to something in the tanks? Any predominant plants or any that boomed or flowered up?
Last edited by steven p; 12-24-2012 at 12:01 AM.