Rats are gonna pee and poop on food. If you mount the hoppers on the wall of the 10 gallon they will climb the sides so it makes no difference (They manage to pee and poop on top of there water bottles). The reason for the hopper isn't to keep the food clean its to make it so they don't waste the food as much. With the waterer's you would be surprised how well they work actually I'm fairly happy with them.