i would not go with a lobster, but you could easily do a red tailed shark. theyre known to nip fins, but none of your current fish have long fins. if you're looking for more of a a mid level fish, it gets tricky. you want something to hold its own with tiger barbs, but they cant be too aggressive or they'll kill the neons. i would say go with zebra danios, or a similar danio. they can out run any barb, wont chase neons, and theyll school with your glo fish