Pet monster crabs, anyone?

[Tired]

TL;DR: let's see your monster crabs that you have on purpose. Sump beasts, in their own tank, wherever you have 'em.

Long version below.

 

I got some really nice live rock that turned out to contain more cirolanids than I wanted to deal with, and wound up neglecting it for awhile, then sticking it in its own little setup to see what popped up. Figured, okay, I can use it as a coral QT tank as long as I put the corals up on a rack so any pest crabs or whatnot can't eat the corals.

 

In the meantime, I was pulling gorilla crabs out of my main tank to humanely euthanize, and I found something neat.

According to Tampa Bay Saltwater's guide, this is Pilumnus sayi, the spine-backed hairy crab. It grows to a carapace size of about an inch. It's a neat-looking thing, and surprised me when I went to pick it up- the hairs are actually sharp, almost like cactus spines. I had expected a fuzzier sensation. Between its neat appearance and the sheer surprise of going to touch it (to get it out of the cup) and encountering an entirely different texture than expected, this little critter won me over, and I kept it in its own container (pictured here) for a little while before putting it into the rock tank.

 

At that point, in March, it was about half an inch across.

These are its last two molts. It is no longer half an inch across. I'm not even sure what it's eating- I'm not feeding it very often, and it doesn't seem to be devouring any of the other life on the rock. I still see tunicates, stony corals, and a couple of bleached rock flower anemones, and it hasn't managed to kill the limpets I'm futilely attempting to keep the tank algae-free with. Maybe it's mostly eating algae and detritus? It's eating something.

This sucker is alarmingly strong. If I feed it something on the end of tongs, it grabs the tongs, too, and holds on tight if I pull. That half-inch baby could lift a rock the size of my fist by holding onto the tongs, and I haven't yet tested how strong it is now. When it gets to full size, I'm going to try giving it some food on one of those fish measuring scales and seeing how hard it can yank.

 

Oh, and I'm still using the tank as a coral and invert QT. With the corals on a rack on the glass it can't climb, and the inverts in a plastic-sided breeder box it can't get into. I've also put a couple of tiny babies that I believe are this species into the invert box, so if anyone in Central TX wants one of these, let me know- I might have a baby for you. You too can have a spiny animal that eats mystery substances and has concerningly large claws!

[Snow_Phoenix]

5 hours ago, Tired said:

TL;DR: let's see your monster crabs that you have on purpose. Sump beasts, in their own tank, wherever you have 'em.

Long version below.

 

I got some really nice live rock that turned out to contain more cirolanids than I wanted to deal with, and wound up neglecting it for awhile, then sticking it in its own little setup to see what popped up. Figured, okay, I can use it as a coral QT tank as long as I put the corals up on a rack so any pest crabs or whatnot can't eat the corals.

 

In the meantime, I was pulling gorilla crabs out of my main tank to humanely euthanize, and I found something neat.

According to Tampa Bay Saltwater's guide, this is Pilumnus sayi, the spine-backed hairy crab. It grows to a carapace size of about an inch. It's a neat-looking thing, and surprised me when I went to pick it up- the hairs are actually sharp, almost like cactus spines. I had expected a fuzzier sensation. Between its neat appearance and the sheer surprise of going to touch it (to get it out of the cup) and encountering an entirely different texture than expected, this little critter won me over, and I kept it in its own container (pictured here) for a little while before putting it into the rock tank.

 

At that point, in March, it was about half an inch across.

These are its last two molts. It is no longer half an inch across. I'm not even sure what it's eating- I'm not feeding it very often, and it doesn't seem to be devouring any of the other life on the rock. I still see tunicates, stony corals, and a couple of bleached rock flower anemones, and it hasn't managed to kill the limpets I'm futilely attempting to keep the tank algae-free with. Maybe it's mostly eating algae and detritus? It's eating something.

This sucker is alarmingly strong. If I feed it something on the end of tongs, it grabs the tongs, too, and holds on tight if I pull. That half-inch baby could lift a rock the size of my fist by holding onto the tongs, and I haven't yet tested how strong it is now. When it gets to full size, I'm going to try giving it some food on one of those fish measuring scales and seeing how hard it can yank.

 

Oh, and I'm still using the tank as a coral and invert QT. With the corals on a rack on the glass it can't climb, and the inverts in a plastic-sided breeder box it can't get into. I've also put a couple of tiny babies that I believe are this species into the invert box, so if anyone in Central TX wants one of these, let me know- I might have a baby for you. You too can have a spiny animal that eats mystery substances and has concerningly large claws!

Very interesting find! I love its color though. 🥰

[mcarroll]

Pretty sharp-looking for a gorilla crab – I love it!

 

Interesting how those spines survive a molt.

[Tired]

The spines seem to form on the new shell underneath the old, as it's hairy again after each molt. I'm curious if they feel different now that it's so much larger, but I don't especially want to touch it at this size. Those claws would probably hurt pretty badly, and it's lanky enough to grab onto me.