[Myka]

They are like wrasses where they are all females, then the dominant one becomes males (opposite of Clownfish). All females have the ability to become males if there is no dominant male around. So, if you get two small ones then one will become male and one will be female, and until they sort that out they will fight. If you get one bigger one and one smaller one (the small one has to be smaller enough to ensure it still is female and not a small male already) then they won't fight as much. If you get a group you will get one dominant male, he will pick a female, and the rest will be outsiders. If the tank is big enough they will break into pairs and have their own little territories. If the tank isn't big enough for that then the outsiders will be killed or generally ignored - it's tough to say how it will work out, and it varies form species to species and individual to individual.

In my experiences with many Yellowtail Damsels in several tanks, they are fairly peaceful to other fish, and do best if you have only two (to pair up) and then they are the only damsels (besides Clowns) in the tank. If you keep them like this then there isn't usually a problem. I've never kept Sapphires, and I've found Yellowtails to be more peaceful than Azures. I also think that any damsels do better in tanks that are at least 40-60 gallons as they will have more space. I find lots of fish that are fairly boisterous are much more likely to become VILE in smaller tanks. Orchid Dottybacks are another example.