Mysterious disease

[Beverly]

If the deaths happened after lights out, I suspect a nocturnal predator. But then you'd see wounds on the fish from the predation, or possibly some sort of slime covering part or all of the fish if water flow is not really high.

[mr_alberta]

How big is the tank? 13 fish could be agression depending on tank size. I'm guessing something stessing them out at night as well. Or it could be a drop in O2 levels...just a guess though.

[michika]

We have a lot of waterflow, and I'm not seeing any slim on any of the bodies. All the fish were/are quite small. The largest fish, is only about 2" in length, and that is the foxface.

I did note today that the foxface sleeps with its hackles? raised, and did exhibit some minor agression towards my tang todaay while feeding.

I'm still having no luck researching what kind of damage foxface posion does on other fish.

[Ruth]

Does your skimmer run 24/7? Could be a drop in O2 levels particularly since it appears to be happening at night.

[michika]

The skimmer does run 24/7, except for when its off for feedings. cleaning, etc.

What causes O2 to drop in the evening? Just the lack of water circulation?