Tank size will really depend on the species. Some of the peacock types only get 6" or so, but L. maculata will get something like 24" or larger. You will probably want a sand bed of some sort, a bunch of liverock, just standard fluorescent lighting will work if you're not going to do any corals. You'll probably want a skimmer of some sort since they eat a lot of meaty foods, I would imagine they can mess the tank up pretty quick, especially with no cleanup crew (they'd be eaten), and a heater.