I definitely agree with Boogiechillin. Lionfish are good fish to keep because they are very hardy, relatively peaceful, and unique in terms of personality. They are also relatively inactive swimmers. As a result, they require less space than other carnivorous fish (e.g. triggers) do. This might be a good news for those who have limited space, but want to keep something unique. The only problem is that it may be very hard to make them accept dead food. But, once you succeed in doing so, everything will go well. Even though their spines are capable of injecting poison into your body, its toxicity level is nothing to fear. So this shouldn't prevent you from having a lionfish. I personally recommend dwarf lionfish because they are less intimidating to deal with than "real" big lionfish. But, if you have a big tank, you can try volitan or radiata lionfish.