It's been a few years since I kept seahorses. I had them with various Euphyllia corals, candy cane, gorgs and blastos. I never had a problem in with stinging . . . vibro finally got them after nearly 3 years . . . I reviewed the threat list and most make sense to me, but blastos a level 2? Maybe it's because they have a mouth? They are about the most layed back coral I've ever kept (and still do) . . . . right next to dun cans.