Do I have a Mantis Shrimp?

DocRose · Jul 30, 2022

Ordered my first every actual ocean rock from Salty Bottom. It's rock from the gulf. We got it on the 27th. Found quite a bit of life with it. Mostly just snails and hermits. We did also get a red mythrax crab. However, I'm concerned there may be a mantis shrimp in it as well. I got 10 lbs. of rock (four rocks). They're all about the size of a dinner plate. One rock has a hole on one side where I constantly see something sticking out, almost looking like legs or claws, but the second I get close enough to the 20 gallon isolation tank, it pulls itself too deep in the hole for me to see. Tonight after lights out I've snuck up on the tank twice with a flash light covered with a red film to try and observe. Each time, the hole has been empty, but as soon as I turn the light on, I hear this clicking sound coming from the tank. That's suspicion number one. I hear it one time, and then nothing, but I've never seen where it's coming from. It almost sounds like the sound you hear when you watch videos of mantis shrimp tapping against the shell of their prey. Which leads me to suspicion number 2. This morning (the 29th) I went down and looked inside and found what I hope is a molt of the red mythrax. However, the clicking sound tonight makes me think it might not be a molt, and that it's actually the crab dead.

Can a small mantis even take on a larger red mythrax? How can I determine if I have one? I don't think a trap will work, because the isolation tank is full of snails and hermits. Thoughts? Suggestions?

toomanymatts · Jul 30, 2022

I have a pistol shrimp and that guy is loud and he starts into his nonsense. Maybe set a small trap and see what you catch.

AydenLincoln · Jul 30, 2022

So clicking is the most common thing with them and fish disappearing but hermit crabs also click their shells too. Mantis shrimp are even known to break the glass and terrorize tanks. I’d say don’t put it back in your tank until you can either capture it and if not I would dispose of the rock or you could do a quick freshwater dip and see what comes out.

DocRose · Jul 30, 2022

AydenLincoln said:
So clicking is the most common thing with them and fish disappearing but hermit crabs also click their shells too. Mantis shrimp are even known to break the glass and terrorize tanks. I’d say don’t put it back in your tank until you can either capture it and if not I would dispose of the rock or you could do a quick freshwater dip and see what comes out.

Well I decided to QT (isolate) this rock for 3 months to see what might have come in on it. That's why it's in the 20 gallon. My DT is a 55g. I hope I can get a positive I.D. on it in that time. Otherwise I might just pull all the snails and hermits out at the end of the 3 months and put them in the DT, and leave the rock in isolation. Which will be sad, since I got it to give my DT more biodiversity.

AydenLincoln · Jul 30, 2022

DocRose said:
Well I decided to QT (isolate) this rock for 3 months to see what might have come in on it. That's why it's in the 20 gallon. My DT is a 55g. I hope I can get a positive I.D. on it in that time. Otherwise I might just pull all the snails and hermits out at the end of the 3 months and put them in the DT, and leave the rock in isolation. Which will be sad, since I got it to give my DT more biodiversity.

I understand and this is one of the reasons why I personally avoid live rock too many unwanted critters. Try looking at night with a red light too you may be able to see other things as when you shine a normal light the animals quickly disappear.

DaJMasta · Jul 30, 2022

If it's a mantis, you will likely see it after a few days. They'll camp out in a rock and peer out at what's going on in and outside the tank, and you'll likely be able to spot it. They'll also hunt towards the end of the light cycle, but before it's dark, and won't generally click after dark, whereas a pistol shrimp will snap in the middle of the night (mine do more than in the day) and will rarely be seen prowling the tank (if their burrow or den is visible, you may see them guarding it from other critters).

My rule of thumb for invert carcasses/molts is that if they look intact, it's a molt, and if they're in pieces, that thing got eaten.

DocRose · Jul 30, 2022

DaJMasta said:
If it's a mantis, you will likely see it after a few days. They'll camp out in a rock and peer out at what's going on in and outside the tank, and you'll likely be able to spot it. They'll also hunt towards the end of the light cycle, but before it's dark, and won't generally click after dark, whereas a pistol shrimp will snap in the middle of the night (mine do more than in the day) and will rarely be seen prowling the tank (if their burrow or den is visible, you may see them guarding it from other critters).

My rule of thumb for invert carcasses/molts is that if they look intact, it's a molt, and if they're in pieces, that thing got eaten.

It definitely looks in tact.

jabberwock · Jul 30, 2022

Contemplating starting a tank with live rock, and following.

Lost in the Sauce · Jul 30, 2022

Guessing it's a pistol. Small ones aren't that loud.

A mantis would likely be out and about by now.

Try a bottle tap for a few nights by the rock.

Congrats on the red mithrax. They are awesome algae eaters.

Duncan62 · Aug 12, 2022

DocRose said:
Well I decided to QT (isolate) this rock for 3 months to see what might have come in on it. That's why it's in the 20 gallon. My DT is a 55g. I hope I can get a positive I.D. on it in that time. Otherwise I might just pull all the snails and hermits out at the end of the 3 months and put them in the DT, and leave the rock in isolation. Which will be sad, since I got it to give my DT more biodiversity.

Keep the shrimp! Lol