i really couldn't disagree more with many opinions in this thread. i have raised snappers from babies to over a ft long. these are really amazing and smart animals. my largest snapper was so much fun. i mainly fed him goldfish and pellets, but he would also eat the odd shrew the cat took home. snappers don't have any territory that I'm aware of. i have raised two snappers together in a relatively small tub for over a year without problems (however you must watch them when feeding as if they snap each other, they don't understand to let go). plus when i find snappers out in the lake, i watch them as they come to the surface to breath; either they have HUGE territory, or they just simply roam around wherever they want without limits. i don't even think they fight each other (because doing so would involve serious damage).
now, if you have a young snapper, go ahead and keep it in a 20 long and with lots of plants and shallow enough water that it can breath just by raising its head up. make sure you have water circulation such as a air bubbler or the water will STINK. learn to understand its body language as it grows so that you can avoid getting a very painful bite. babies don't hurt when they bite, but as they grow they get stronger fast.
and to my knowledge, snappers wont "stink" when they get older as long as their kept in a clean aquarium. and i don't recommend keeping snappers over a foot long (shell length) unless you have a serious sized home for it.