Fish food and deodorant

Question

1) The first ingredient in my fish food is wheat flour, so can I use it. Does fish food need to be kosher l'Pesach. Fish food is definitely inedible, but since there is an issur of "mashehu" I thought that any amount of chametz, whether edible or not, may be a problem. 2) Does the issur of mashehu mean that even inedible foods are asur behana'a during Pesach? 3) Can one spray deodorant on his close on Shabbat, since it will make the clothing smell? 4) Can one rub stick deodorant on his undershirt, since it will make it smell good?