Monk and his son were being housed in a 20L tank. This is how I house rats, currently. I'm in the process of trying to get another rack built (I currently have one with only one functioning tub since the runners are not on)

10g: 1 pregnant/nursing mother, 2 1-2 month old rats.
20g Long: Up to 3 (no more) fully grown adult breeding rats, normally a 1.2 group. If younger, no more than 4.
Rack Tub: My rule is no more than 3, but I've never housed more than two to a tub so far.

I'm trying to think of a way to give them more ventilation than a tank can provide. I don't like tanks either but its all I have right now until I get my racks built.

Update: He had decided he doesn't want to eat any solid food at this point. BUT, he loves the "gravy" from his mixture. The "gravy" includes water, the gravy from the wet food, ground up dog biscuit, and tiny bits of lab block. He loves it and has downed 8ml of the liquid. We have made him a little nest in his bucket. Its a green bucket that we usually use to weigh the snakes. We lined the bottom with paper towel and gave him a clean shirt.

*Just thought I'd add. He peed on me. So he's taking in fluids ok.