I Think I Got a Mantis In My Tank

Rcpilot

Rcpilot

Reef enthusiast
Yup! I can't really tell what it looks like, but it's a shrimp and it's dark gray in color. The problem is--the little bugger is only about 3/4" long. It lives under a frag plug that I set on top of a small rock. The rock is about the size of your fist, but it's kinda flat. I put a round frag plug on top of the rock so that my zoas could spread out. There is a gap under the plug. I spotted some kind of little shrimp inside a hole between the frag and the top of the rock. He only comes out at night. Can't figure out what he's eating because I need a flashlight to see him, and he runs away everytime he sees the light.

I'm not real familiar with shrimp. He sure is fast, and he rolls up in a ball and slithers up inside a hole where I can't see him. His body movements sure do look like all the mantis shrimp I've seen. Looks like he's gliding around.

Are there any other type of shrimp that are dark gray (maybe black) when they are small? Nocturnal?

Wondering what to do. I could drop the whole rock into a bucket of fresh water and kill it. But, if it's not a mantis, I'd feel bad. Don't like killin' stuff in my tank unless it's really a bad critter.

I could drop the frag into a bucket of saltwater and hope to shake him out, or bait him out with some krill or brine. Then remove the frag when he comes out in the open.

Maybe let it grow a bit and try to get a better ID later? No guarantee it will stay in this rock though. It could move and then I might not ever find it again.

Any thoughts?
 
Mantis shrimp aren't actually shrimp. They are mis-named. Plus, they come in all sorts of colors, so it could be one...

Does it have eyes on the end of stalks??
 
Are you hearing the dreaded ''clicking'' sound?

If so,its a mantis or pistol shrimp.The only mantis that worries me are the smashing(thumping) mantis and not the clicking kinds.
 
I don't hear a clicking sound. Can't see the eyes. It does have "antenna" It's so fast. Been trying to sneak up on it with a flashlight, but as soon as it gets hit with the light--it's gone. I held the light for about 5 minutes to try and acclimate it. It did finally come out a bit, but it's so small, I can;t really make out the eyes or head shape. I was looking for the front "arms" that are typical of the mantis. Can't really get a good look at it.

Wish I could get a pic, but it's so small.

IF it is a mantis---what harm can it do right now? Will it eat my zoas or mushrooms? Will it eat small (1/2") blue leg hermits?

What IS it eating? Copepods?
 
It will for sure be eating your cleaner crew, including crabs and snails. It's not going to go after corals, but it will go after any small fish that you have.
 
Biff don't get Rc all worried,just yet.

There are only a few species of mantis that does what Biff mention.Most just scavenge dead animals.Your know if its a smasher-there will be shells of dead snails and crabs near its den.I believe only the smashing kind are really dangerous.Maybe you have a baby lobster or shrimp since you haven't heard any noises.
 
Use a red light to sneak up on it. Inverts can't see the red light so he wont know your there unless you make too much movement around the tank. Good luck finding out.
 
Okay, it's NOT a mantis. No eye stalks. No clicking. No carcasses lying near the lair. :D

And I have at least 2 of them. :shock: Just saw the second one by shining a light in the hole, and there are at least 2 of them in there. They are definitely shrimp or lobsters. They are dark gray in color. Eyes are attached to their heads. I can see the glow in their eyes when I hit them with the light -- if they look at the light.

Hopefully are not dangerous. What does a mysis shrimp look like? Or a juvenile krill?
 
Mysis are pretty small and I think stay around a 1/4 inch in size. Maybe you got really lucky and got two pistol shrimp. If so you could add a goby and maybe they will team up!
 
I'm going to rule out mantis because I never heard of mantis living in groups or pairs.Besides your not hearing any noises,nor finding shells around.

Ruling out pistol too since there's no clicking noises.I'm going to say mysis and krill don't come as hitchhikers.Mysis and krill are cold water,mysis are to small.

Dark gray?It sounding more like small lobsters or a different kind of shrimps.Get them out and take some shots.I like to see these guys.
 
Here is a video. The best movement and shot is in the first 2 or 3 seconds and again at 1 minute/23 seconds.

Sorry about the quality. I'm holding a flashlight and the camera is set on top of a pile of books to get the right angle into this 1/2" hole. For reference, the zoa stalk you see in the frame is about 3/16" thick and the heads on these zoas are around 1/2" when they are fully grown. The shrimp can't be more than 1/8" thick and about 3/4" long.

 
I would have to say that sounds just like a mantis. They can be many shades of dark or bright colors. They do the little ball roll thing when they change directions or go into hiding. The eyes arent really on stalks on mine, maybe 1cm stalks if you would consider it that. Its still small though, Ive never heard my mantis click. It ate a whole goldfish yesterday the size of my biggest clown with ease... Mantis could live in pairs, depending on the species, but usually dont. maybe they hatched together as hitch hikers and some how get along? I would remove the frag and try to get it out before it gets any bigger. try it in saltwater and see if it will come out and trap it.
Here is a pic of my Mantis, there are around 300 species if I remember correctly, this one can even change colors depending on what color environment its around when it molts. Does it look at all like this basic shape? If its one like this its a slasher, you shouldnt hear clicks. At least I didnt when it cut the goldfish in half...

 
That video looks to me like a mantis... Same rolling action when changing directions. Pretty small so probably not a murderer yet, at least not that you have noticed yet. Even if im wrong, im sure it cant be too good, or people would buy them and have them in their tanks... my guess is a baby mantis though.
 
They do roll around like a mantis. But, I'm not sure if ALL shrimp move like that. I don't know enough about shrimp to say one way or another. Maybe ALL shrimp DO move like that?

Here is a better video, but after the first 10 seconds--they don't move. You can watch the whole thing if you want, but they just sit there.

 
Thats it Reeffreak!

They look just like the pic of the Gammaridean amphipods shown in the article. Mine are just darker in color.

Okay, so are they reef safe or do I need to kill the little bastards? Could they serve as a food source for my 6-line? Should I put them in the refugium? If I put them in the refugium--will they eat and destroy all the copepods in there?
 
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For the most part they should be reef safe.I read on few that may much on corals.I don't know how true that is.I have exactly the same thing,some are really small,maybe 1/8'' and some huge 1/2'.I believe they are beneficial-detritus eaters.I see my anthias picking some big ones from the glass,rocks and sand.I put them in the fuge if possible,maybe they are maiting.I'm sure their babies will make good food for your sixline.
 

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