Ok, I have 3 blue/green reef chromis.
Up until two days ago they schooled and ate happily, paling around with my clowns and getting daily 'baths' from the cleaner shrimp.
2 days ago, one of the chromis took to hiding in the rocks, in a deep fissure at the base of the tank, only poking it's head out when it thinks I am not around, but never leaving the crevace.
Another of the 3 is basically standing guard above the entrance...hovering around mid way up the tank, always in that area.
The third is happily flitting around the tank without a care in the world.
Neither of the two 'odd' chromis does a blasted thing when any type of food is introduced (and I give a well rounded dose at feeding time..they usually are pigs..).
The one 'on guard' shows no visible signs of infections or duress, but simply wont leave that general area and will not feed...
My only thoughts are that they have gone insane or they have potentially spawned and are protecting their eggs until such a time as they can let the youngins hatch or something...
Taking the guard out and into QT wouldn't be much of a problem...the other would be impossible without tearing the whole reef apart...
Nothing new has been introduced that would be percieved as a threat, so that can be checked off the list..
Any ideas or suggestions?