My husband and I recieved our 5 Yellowtail Blue Damsels, about a week ago. 4 are about 1 1/2 inches in length and one is about 1 inch (if that, it's a tiny one). Here in the past couple of days of watching them closely, we've realized we have an Aggressor. One of the larger ones has completely nipped the fin off the tail of one of the other larger ones. He's also taken a chunk out of anothers tail fin. So that's two that have damaged tail fins. The fourth largest just trys to stay out of the way. The Aggressor keeps all the other larger Damsels at the top of the tank and on the opposite side from the smallest. The Aggressor will then swim over to the smallest and they will slowly swim circles around the rock formations. If any of the other fish come to the side of the tank where the smaller one is, the Aggressor will immediatly chase them off. I've also noticed the Aggressor, only when close to the smaller damsel, will turn almost black then change back to bright blue. It only lasts for a couple of seconds. I also caught the smallest picking up the crushed coral at the bottom of the tank and spitting it out in another location. Surely they are too young to even be thinking about spawning!? I know Damsels are semi-aggressive, but this behavior is strange to me. What does the color change mean? Should we take the Aggressor out? and how will this effect the smaller Damsel?
Thanks, Mrs. Sheets
Thanks, Mrs. Sheets
. But I use Bing. Guess I need to go back to Google. It didn't seem real that they were preparing to spawn until lastnight. I saw the Aggressor swim over to, "the spot" do a shaking movement and scattered the crushed coral. I looked at my husband and said, omg, they're preparing a nest! I thought they had to be full adult size to spawn. Guess I was wrong on that too. lol Anyway, Thanks Again for the Link! 
