In my 20 years of reefing, I’ve never had too much trouble from yellow tails. Now, three/four stripes and dominoes, those guys are awful, but IME so long as there’s adequate room/territory and more than just one or two other tankmates, they’re not too bad. Also never had one bite me. In a 15g, you’d have to be careful with tankmates, but I think yellow tails get a bad rap.Please tell me you didn't get a yellowtail damsel. They are the meanest bullies in any tank and they bite whenever you put your hands in the tank. Most damsels are just mean---yellowtails are evil. By the way, a two hour drip acclimation is long for even the most sensitive, rare invertebrate. For most fish, you can usually just temp acclimate in a their shipping bag for 15 minutes, then add a some tank water into the bag every 5-10 minutes for 30 minutes until you have a 75% tank water/25% shipping water mix. For a damsel, you probably could get away with just temp acclimation and then pour him right in.