I have purchased small groups of blue chromis over the past month. The first was a group of five, lasted about a week. The second group of three lasted less than 48 hrs. I found most of them being eaten by hermit crabs. they all seemed happy and fed after being intruduced to my tank. I acclimate all of my fish and have no probleem with the health of the other fish. 29 gal bow 20 lbs. live sand, 30lbs. live rock moderste to high water movement and an air source. 1 Cardinal, 1 Lawnmower Goby, assortment of snails and hermit crabs. feather dusters and a LTA. I found one this morning swimming erratically and his mid section was red. Water tested two days ago before acclimating the new fish showed all safe ranges. nitrite, nitrate, ammonia, ph, phosphorus, and salinity are all in the correct levels. What can it be?