Bartlett Anthias Die off

[Pikeman]

Over the past three days 3 of my 4 Barlett Anthias' have "disappeared" (died) in my tank and the remaining one looks very weak. There was one male and three females. They have been in the tank for about three months. Up until a few days ago they were all healthy and vigorous, then they started to hide during the day and finally they're gone. There are no predators in the tank, nor have there been any significant changes to the water quality. My nitrates are barely detectable. All my other fish are behaving normally and I do not see any obvious visual signs on the remaining one with the exception of the weak swimming/more hiding as with the others. Any thoughts?

[blstravler]

What type of lights are you running?

[Pikeman]

I have 2 - 250W DE BLV 10K MH's and 2 54W T5 actinics. I run the MH's for 7 hrs a day and the t5's for 12.

[SDguy]

How much/often were you feeding? Also, even with no obvious aggression, they could still have been intimidated by other fish. What other fish are in there?

[Pikeman]

I was feeding primarily once a day with Formula 1, Formula 2, mysis, and cyclopeze. They received a big feeding.

Other fish in the tank are two ocellaris clowns, 1 sailfin tang, red hawkfish, a marine betta (medium sized), and a Banggai cardinal.

[blstravler]

Over your DE bulbs do you have a glass sheild?

Did the hawk fish get nasty?

Where the anthias very thin when they died, might have needed more feedings?

[Pikeman]

Yes, the lights have a glass cover.

The hawk fish is very docile as are all the other fish in the tank (150gal) with the exception of the clowns and thats only if the fish approach their nesting sight.

I thought about the feeding once/day issue versus multiple feedings, but the anthias' rapid decline in health didn't lead me to think it was malnutrition. In fact, as they starte to hide out, their feeding became very weak. One would think they would be more aggressive in their feeding as they normally were. Again, it was the reletively rapid decline that raissed my initial question.

I also watched the remaining fish very closely and could not identify any parasites, skin blemishes, knocked off scales, etc.