Lionfish are hardy, easy to come by and make a good addition to the aggressive fish tank. Dorf lions are pretty hardy. I would not recomend getting a batfish. These grow very fast and require a large tank with unobstructed swimming space. Batfish are best left in the wild or to large public aquariums. As far as ordering fish online, when your order multiple fish it pays off. If you are looking for only one get it from your LFS
. This way you can pick it out yourself and you do not have to pay shipping. Ordering fish online pays off when you order a lot at one time with only on shipping charge.