My mice don't smell and I clean them once per week. No vanilla in the water as of now. I used to use baking soda sprinkled generously on the bottom of the tanks(mostly ten-gallons and a few lab cages), but now that I switched to a 100% hardwood bedding that I get at Tractor Supply(it's not all pine as I can tell from the smell and its lack of irritating my skin or the mice). It's around $4.50 per bag and the bag is 5 cu. ft.

I now have 2 cages(10 gallons) of 1.3 and one with 1.4, all of which have had babies(hoppers now) and are pregnant again, then I have 3 other lab cages that each have 1.1. One of the lab cages(long haired agouti/white) has babies and is pregnant again(VERY, LoL) and the other two lab cages are just pregnant and waiting.

I keep all of these cages in a small room at my school, the size may be around 6'x4.5'. There is only a smell of bedding and lab blocks when I enter the room. I have noticed though, that if there is a cage of only boys, or a single boy, then they STINK. They like to musk on everything and it is gross. If males are kept with females, 1.1, 1.2, 1.3 or 1.4, then they DON'T stink for some reason. No competition I guess.

Neutering mice just doesn't work well. They are too small and the amount of blood in their body is very minute, plus maintaining their little bodies under anesthesia(and constructing a mask to fit their faces) is sometimes difficult. There is only so much space you can work with. If you got them from a petstore, it is extremely unlikely that they are sterile.

If they are having problems getting pregnant, you may need another male that is older, or they may just not have gotten used to each other yet. Sometimes it takes the male a little bit to figure things out. You have checked to make sure there are males present? Sometimes when they suck those things up in their body, it can be hard to tell.