Burrows in my sand

Hi All,
I have a 300L tank that I have been cycling for the last 8 weeks. There was only live rock for the first 4 weeks (~30kg) and then I added a stromb snail and a trochus snail to clean up some of the diatoms.

At the 5 week mark I went overseas for a 2 week holiday and left all lighting off during this time.

When I returned home, I found my stromb missing. I have also noticed quite a few "burrow" looking holes in the sand around the base of my live rock. The entrance holes are between 1-2 inches across and there are at least 4 that I can see. I have also noticed a clicking sound coming from the tank on occasion.

The rest of the tank is in great condition, all of the parameters are good
pH 8.2
Ammonia 0
Nitrites 0
Nitrates <25ppm
Salt water density is 1.023
KH is 11
Phosphates 0

Could the burrows be my stromb (sand bed averages about 2 inches in depth, not live sand) or could I have a mantis shrimp lurking about? Is there something else that may have hitchhiked its way into my tank that is burrowing around?

I have tried to take some photos of the holes/burrows that are easiest to see but the quality of the pics are not great.

Any suggestions anyone?

 

My strombs often bury themselves and i dont see them for days. Could be him.

 

Could you possibly have picked up a pistol shrimp? They burrow and make a very loud "pop" noice with their claw....

 

Put some food near the opening of the burrows. If it is a Mantis, it should come right out and try to grab it. They are quick little buggers! I used a trap for a mantis to catch mine, and then moved him to my 'fuge.

 

As soon as i read the part about clicking, my heart stopped and i began to panic..... i think im beginning to take this hobby too seriously.

But seriously, i hope its not a mantis.(sounds like it might be one)

 

If it's a pistol shrimp, you generally hear a single pop. Mantids often use multiple hits, so you might hear "pop-pop-pop" rather than a single "pop".

By "stromb", I'm assuming you're referring to a Strombus sp., such as a fighting conch? If so, they can disappear for long periods, as mentioned.

 

Thanks guys, I do hear multiple clicking happening. I don't really have anything in the tank at the moment except for a hairy mushroom coral that hitchhiked its way in on some live rock and a bi-colour blenny.
I will try some food in front of the burrows and see what happens.

 

Multiple clicks (pop-pop-pop) suggests that you may have a mantis in your tank, while single, spaced clicks suggest a pistol shrimp.