Have Crab; Worried about Fish

[ToddTT]

I picked up a small Scooter Dragonet about 10 days ago. He looks just like this:

I hadn't seen him eat anything, it looked more like the poor thing was just poking around and not finding anything.

So I decided to get a "fresh" piece of live rock at my LFS tonight. I already had a small amount of rock in my tank, but after years of neglect I don't think they are very live any more. And I haven't seen any little critters running around in my tank for years.

As soon as I put the new piece of rock in, the scooter hopped on it and started grazing. I was quite pleased with my generous gift, and cleverness, until...

An inch away from the scooter, a few creepy legs started to emerge from the rock. Attached to these, the most hideous monster you could imagine. Or, possibly, just some garden variety crab. ;)

I'll try to get a picture, but that crab doesn't like to make himself visible.

But imagine a small scooter, about an inch. And a small crab, with a body the size of a shirt button. But if he extends his ghastly legs he is about an inch wide as well. Maybe 1.25 inches.

Will this crab be a threat? Does he want to grab and chew up live fish, while they sleep? Or will he be more interested in uneaten food and other nasty stuff in my sandbed?

Should I try to capture this little monster and relocate him to my overflow, or sump? And if I don't, is Scooter a goner? Not to mention my firefish?

What have I done?!?!

Or is everything okay? Please respond ASAP so I can go to sleep. ;)

Thanks!

[ToddTT]

This is Scooter, pardon the blurry camera work (click for the full size):



This is the crab. The opening is about the size of a penny:



By the way, anybody know what kind of algae that is in the first pic? It sprouted out of nowhere!

[leebca]

I moved your post into the Reef Forum where they often discuss invertebrates. Someone there might recognise the one you have found.

I would say one thing, and that is you really don't want to add live rock to an established aquarium without putting it through a quarantine process to make sure it has fully cured (at least) and to find hitchhikers like this.

[ToddTT]

Thanks Lee. I plan on setting up a QT before putting anything else in my tank ever again.

And as for the crab, he has proven quite elusive. I have trapped him in the rock for the moment, and will hopefully be able to catch him and return him to my LFS, or give him away.

[blennydude]

Todd, does your scooter eat frozen brine, or mysis shrimp? If not you can train him to eat them w/ a fish net w/ food stuck to the sides and put it near him so he can examine them til he starts picking them off the net. They also need copepods on occasion which is what he is looking for when he scoots around the bottom. That is a whole other issue to tackle to get them in your tank. I have a pair of scooters, male/female and they do a mating dance together at night that is really cool to watch. You know a male from his large sail like dorsal fin that he raises when he is in the moment. yah baby, you go little scooter.

[ToddTT]

Todd, does your scooter eat frozen brine, or mysis shrimp? If not you can train him to eat them w/ a fish net w/ food stuck to the sides and put it near him so he can examine them til he starts picking them off the net. They also need copepods on occasion which is what he is looking for when he scoots around the bottom. That is a whole other issue to tackle to get them in your tank. I have a pair of scooters, male/female and they do a mating dance together at night that is really cool to watch. You know a male from his large sail like dorsal fin that he raises when he is in the moment. yah baby, you go little scooter.

He has grabbed a couple of mysis shrimp in the past week, but using the net to feed him is a great idea! I'm going to try that today. And judging from his personality, I bet he will be the first to venture into the net.

I had also bought some Arctipods (expensive!), which he seems to ignore when I squirt them in his vicinity. Although I imagine he finds some after, that have settled on the bottom or on rocks.

I don't have a copepod population to speak of... have you tried any live copepod products?

I think he is a male... I'll get a closeup photo and post it. If I can get him a "playmate", I definitely will!

Thanks,
Todd