My mice have to eat their chow through hardware cloth nowadays, but before I just dropped it in a bowl when they were in aquariums. They ate it up and I added more.
But I have noticed with the dozen or so weaner mice in the 20 gal I've got, they collect the chow blocks and stash it all over in a corner where nobody poos. My rats do the same thing, empty the bowl and stash it in a clean corner.
I tried the bin style feeders for ferrets, and they worked ok, but the nasty critters climbed to the top and pissed all down the sides. After a few weeks it eventually reached the food in the tray at the bottom. I was never so happy to have a rack than to end the slimy water bottles and bins. If they want to piss on their own food, they can do it on the floor. =P
Like Carol, I do suppliment their lab blocks with high quality dog/cat food (Nutros) once a week when they got cleaned out. Has good omega fatty acids for pregnant females (or so the human baby books tell me).
But your setup doesn't look at all unlike mine when I started out. Although mine were in a 20 gallon longs. The bigger the tank, the less often you have to clean it out. But at least Aspen Supreme works great for that. I just wish it wasn't so heavy on my rack tubs.