I have a lionfish tank:
http://www.malawimayhem.com/gallery.php?id=134
http://www.malawimayhem.com/phpBB2/v...light=lionfish
As far as keeping them, they are not messy eaters as they generally swallow their food whole. As some species get fairly large, they can be a big bioload on your tank, so a good skimmer and filter are important, as are large waterchanges to keep nitrAtes low.
But, IMO, they are one of the hardiest and easiest fish to keep, so if you want that, they are a good choice.