what's so messy about the rats, exactly? Their intestinal contents spilling out, or the blood, or the fur? and did you feed RATS or just mice? I love the ducklings idea, sounds awesome.
I feed my 200g and 55g cichlid tanks (the species comprise of a couple smaller CAs and a dozen or so african rift-lakers, and everythings in the 3"-9" size range) anything that moves. I feed them mummichog killifish, tetras of all types, smaller barbs of all types, danios, small gouramies, red claw crabs, ghost shrimp, small gobies, livebearers of all sorts, an oranda goldfish, and, well.. pretty much anything that's readily available at a LFS at a relatively inexpensive price
The faster fish species (tetras, danios, fathead minnows) are fun to watch because they are so fast; they make for awesome chases.
A certain LFS got some exodons in recently, selling em for 6 bucks apiece, I've been meaning to head over there and throw some of those guys in; everyone says they are greased lightning.
I'd like to buy some african dwarf frogs but those things cost 7-8 bucks everywhere, and being a mere college kid I do have my monetary limits for spending.
One recent spectacle I witnessed was my throwing a 3" male sailfin molly in the 200g. I had bought the molly, who was the dominant fish in its tank at the lfs, for 6 bucks, in the interest of keeping it as company for a 4" mummichog in a 10g. Those two fish battled one another for dominance for about 2 weeks, the victories going back and forth, and while the mummichog had the undisputed physical superiority, the molly just would NOT relent, and in the end the mummichog found itself unwilling to make full use of its physical capabilities, and relented to the molly for good. After seeing about a week of that, I decided to plop the molly in the 200g, since I was much more interested in the mummichog.
That molly made for quite a show; it only lasted about 1 minute for him, but that full minute was full of fascinating strife. Upon hitting the water, it raised its sail up and shook its body in defiance, but my 3"-5" africans sicc'ed upon it like a pack of hellhounds anyway! I mean that molly literally recieved bites from all sides at once. The africans fought amongst each other for this sail-up-pissy-looking molly like it was already a dead fish, and each african took turns taking the best jaw seizure and shaking/thrashing this molly up while the others desperately tried to seize control of the molly's body. Its big pretty sailfin was utterly nonexistent in about 20 seconds, and after a minute or so the molly was ravaged beyond all hope, and drifted about lifelessly while the struggle for its body endured. It can take my fish about 20-60 minutes to fully dismantle and consume a fish of this size; they're only cichlids after all, jaws aren't really designed to bite like a piranha.