What would tear a zoanthid wide open?

[redfishsc]

Woke up this morning and my "ring of fire" zoanthids were all closed (and they still are), but otherwise plump and healthy...... except one.

 

It was flayed right open, almost like someone popped it like a balloon.

 

 

I have small whelks in my tank that I remove as I find them, but there's always that one that I missed. Could this be the culprit?

 

 

I haven't added any zoanthids to the tank in 6 months, except one small frag a month ago that I inspected well, and I haven't seen any nudis in the tank, even at night.

 

 

What could have happened here?

 

Water parameters are pristine.

 

0.0ppm nitrate (salifert)

0.05 or less phosphate (seachem)

salinity 35ppt

temp 79-81

alk 14 (kinda high, I know)

 

 

Light is a 4X24 NE with 6 month old bulbs.

[cheryl jordan]

Do you have any shrimp or crabs?

[kurtl000]

Most inverts with claws will rip open a coral to get at food.

[carbon-mantis]

I've had a blue leg hermit do that once; stuck his leg right through the thing's mouth and disemboweled it.

[Seiryoku]

I've had a blue leg hermit do that once; stuck his leg right through the thing's mouth and disemboweled it.

 

Another reason to add to my list of reasons why I hate blue leg hermits...

[redfishsc]

I do have blue legs. However, these zoas are mounted to a Magfloat sticking to my back glass.... I'll have to watch and see if any hermits can climb up the glass on the algae and get to the zoas.

 

 

 

Only about 1/3 of the colony opened up today, which is totally weird for them. These are some fast growers and showy.

[Bio-Reef]

If you have snails, the crab probably got on the snail and the snail went up the glass and the crab got off at the zoas. My crab hitchhikes like this all the time.