damsels

Question
Paul--I recently added 3 blue damsels to my 55 gallon saltwater tank.  One of the damsels is behaving oddly, sitting on the bottom, not moving very much (even when I place things near him--net, cleaning magnet, etc), not eating, etc.  I have a well-established (2+ years) tank with lots of live rock & sand, 2 other damsels, a coral banded shrimp, an emerald crab, a few hermit crabs & about 10 various snails.  Water paramiters are perfect, I checked the salinity, Ph, ammonia, nitrate & nitrite levels earlier this evening.  Temp is around 80F.  I have a 4 wheel bio-wheel filtration system, with additional carbon.  I also added some Amquel tonight to eliminate any toxins that may be in the water.  Any ideas as to what might be wrong with the damsel?  It doesn't have ich and didn't appear to be stressed at all (until now--all 3 were added last Thursday evening).

Answer
have you noticed any aggression toward him from the others? they are very territorial, after they have claimed their patch of reef (they usually require a patch of 50cmX50cm) they will defend it to the death.

it could be there is not enough reef to go round and he is left without any. he may also have been sick at the fish shop, there could be any number of things.