Suicidal hermit?

Life would be a lot simpler if the animals could talk. Take my small community of intertidal critters, for example. I keep a close eye on them, checking their water quality and temperature daily, making sure they're enjoying their food, they're happy and healthy. Are the hermit crabs all busy; are they waving their flags about, not fighting? Is the big anemone open for business? Are the bubble shell snails still mating? How about the leafy hornmouths; do they have enough barnacles to eat? And so on.

But if something changes, how do I know what's gone wrong?

There are currently 38 hermits in the tank. That means that every few days at least one of them molts. The usual procedure, then, is that the newly-soft hermit climbs up into the seaweed, out of the range of hungry crabs, until he hardens off. An hour or two later, he comes down again and selects a new shell, slightly larger than the last one he was wearing.

I found a mid-sized hermit in the eelgrass a few days ago. His leftover molted legs and carapace were on the weeds below.

New, fresh, clean skin and hair. Now he needs a new shell.

A few hours later, he was still on the eelgrass, still nude. That wasn't right. It's not safe; the crabs were already patrolling beneath him. A freshly-molted hermit belly is a highly-prized delicacy, and they weren't planning on missing out.

I shooed the crabs off to the other end of the tank.

Later, finding the hermit still naked, I caught him and put him in a bowl with a selection of shells. In a couple of minutes, he had selected one and climbed inside. Good! I put him back in the tank.

In the evening, there he was back up in the eelgrass, without the shell. Why? That's asking for trouble!

I found him a different assortment of shells and gave them to him in a bowl. Again, he got dressed immediately. Maybe the last shell was just a bit too small. Back in the tank.

In the morning, he was in the eelgrass, nude. The crabs were back, watching him.

Three more times, over two days, I took him out and presented him with good shells. Each time, he put on a shell, then discarded it as soon as he was back in the tank. Why, why, why? Talk to me, Hermie!

His abdomen is reddish purple; some have green bellies. The barbs at the end hold the shell in place.

Laurie said that maybe he was itchy. Maybe he'd got fleas. (Copepods and/or mites? Possible.)

Then Val, the big anemone, started shutting down, pursing her mouth disapprovingly. She does that if the water's not quite up to her taste. I've been changing it regularly; the last change was only two days before, but if there were too many mites . . .

I took everything out of the tank, scrubbed the walls (goodbye copepods) and triple-rinsed the sand. Cleaned the pump, discarded old eelgrass, scraped off invading orange-striped anemones, removed two big worms and washed off their slime. Filled the tank with new water, well chilled; replaced everything. Hermie went back last, in a nice new shell.

Fingers crossed.

Two hours later, Val was happily feeding, and Hermie was still in his shell. Tonight, he's still ok.

Yay!

The little blue anemone, on clean eelgrass. Eats hermit food; likes shrimp.

But it would have all been sorted out earlier, if he'd just thought to tell me he had an itch.