In my experience, Yellow tails are the "nicest" damsels & chromis only pick on other chromis. A maroon would be the boss of the tank, if it's big enough. But how many damsels, since this is a fairly small tank. You'll have to consider the bioload. <of course, this is an obvious case of "do as I say, not as I do"
> A yellow watchman should be ok in terms of ecological niches, since it'll stay on the bottom, the maroon will mostly be mid-water & the damsels more surface fish.
Just my $.02
Anthony