Ha, simply asking if it was a Conch, tiger, fighting, just a loose guess based off the shine the shell seems to have.I do not know exactly whats Conch means - this is one that should be specialised at detritus and organic leftover. Do not remember its name. It could be an Olivia spp
I had a Seriatopora colony die overnight a few weeks ago. A day (or two, can't remember for sure) before we had had a particularly hot day and the temperature spiked to 82.5°F. At the time I was keeping the tank at 78°F. There are two other colonies of the exact same Seriatopora in the tank and both of those survived. The one that died was getting the least amount of flow as it's shielded by a large toadstool coral right next to it. No sign of anything like brown jelly though.I spoke to Lasse today at work, but I'll write my theory here as well(plus remind Lasse about the name of the coral..)
We have a lot of Seriatopora at the Aquarium, S. hystrix, S. guttatus and S. caliendrum. I believe the colony Lasse had was a S. guttatus.
They often grow fast and when they reach the surface, the branches gets closer and closer in the upper part of the colony. Sometimes after a stressor(like high temp or power break), but also sometimes without any changes that I know of, these colonies gets a brownish slime. Looks the same as when Euphyllia gets brown jelly disease, perhaps it's the same.
The disease spread fast and in a day a 15 cm colony can die. Usually just leaving a white skeleton.
This has mostly happened to large colonies close to the surface, often where there isn't much room left between the colonies/branches. Perhaps low water flow together with high levels of light is a trigger.
So my guess is that the colony got brown jelly disease while you were away. Or maybe it just missed you too much
Now clean the skeleton and bring it to work. We need media for the calcium reactors.