i have the eco mist(away from fish tanks)and no deaths(fish tanks are also covered) and when the can runs out we spray flies but first we cover all tanks and open windows coz it very strong smelling(i dont buy the odourless one coz i dont no how much the room has toxic in it)but then again the ecomist runs 24/7
i have the ecomist in lounge with one fish tank,two dragon tanks,fish bowl in kitchen,dragon tank in dining room and the other fish tanks are upstairs plus all the live food are stored in cupboard under tank and no deaths there too but now that i think about it our house always has all the windows and doors open so that will help ventalate it
just saying i have no problems with fly spray(and when we run out we have loads of flies)