What's piling up the sand? - Mystery critter SPOTTED, still NOID

[ThunderGoose]

I've noticed mounds of sand forming in my nano tank. Hitchhikers' Cove was started with live rock so I have all sorts of mystery critters. This mound gets larger every day and is NOT where the current would pile up sand. When I clean the tank )and knock it down) I find it popping up again, sometimes in a new spot. Now it's up against the glass and there's a tunnel which may or may not be related. All ideas are welcome.

American quarter for scale.

 

[Gator0930]

What kind of livestock and CUC do you have?

 

[kirstyflash]

Is that dragons breath? If so I’m jealous

 

[starypotter]

I'm sticking around for the answer that's neat.

 

[chefjpaul]

Love reefing mysteries

 

[Evan28395950]

Following

 

[ThunderGoose]

Livestock that I've added: masked gobies, flaming prawn goby, sexy shrimp, Pederson's shrimp, blue leg hermits, a few snails (astrea and cerith), candy striped pistol shrimp (who lives under a rock at the other end of the tank), large coco worm and a large feather duster - corals are mostly gorgonians and yes, that is dragon's breath macroalgae. Everything else is a volunteer. I know I have several small crabs of unknown identity but other than that... I dunno.

 

[kirstyflash]

Could be the pistol shrimp if he travels but if you’re sure he stays in the one place...ours thinks all the rocks are his and does the rounds.

 

[ThunderGoose]

I don't think it's the pistol. She has a lot of excavations under a couple of rocks but this sand pile isn't near any of the tunnels I can see and it's not piled up right by the rock. Plus she doesn't produce hills like this near her favorite rock. I'm gonna clean the tank this afternoon and we'll see if it comes back, how fast that happens and if it's in a different place.

It amazes me how little we know about what's in our reefs, especially when you start with live rock.

 

[ThunderGoose]

I cleaned the tank on Sunday and this morning noticed a hint of a pile. This afternoon - it's back.

When cleaning I did not uncover any obvious cause for this structure. I stirred up the sand bed and destroyed the old pile. This is about 4 inches away from the original spot. I do see a hint of a tunnel inside the mound - which I also saw last time. Maybe the shrimp is traveling but why would it create these mounds away from the rocks? It's about as wide as it is high and notice that the sides are somewhat steep. I don't see that with the snapper's excavation debris.

There is a small pile of sand near the snapping shrimp's favorite hangout but this is on the other side of the tank and not near any known shrimp tunnels.


Huh.



Maybe... Maybe it's

Tiny

aliens.

 

[reef lover]

Have you checked after lights out with red light?

 

[ThunderGoose]

Sorry to disappoint but several red light session late last night and early this morning showed nothing... Still a mystery...

 

[rainmaker]

Could be mantis shrimp

 

[reef lover]

Strange...

 

[kirstyflash]

Sorry to disappoint but several red light session late last night and early this morning showed nothing... Still a mystery...

Don’t know if it’s the same for you but in Australia ‘red light’ and ‘sessions’ in the one sentence has a whole other meaning!

 

[Holy_makerel]

I had similar mounds in my nano. Turned out to be some sort of worm that was doing it.

 

[Jay1982]

When you clear off the sand, how long does it take for the mound to develop into what is pictured?

 

[ThunderGoose]

FINALLY spotted the culprit.

When I leave the sand around the mound alone it gets really big (bigger than in the picture - a good inch and a half above the sand bed and maybe 2 or 3 inches wide) and shaped like flat top pyramid. Last weekend I stirred up the sand bed and the mystery critter moved to the side of the tank where I can see it while I'm at my desk so I finally got eyes on it.

As @Holy_makerel said, it's a worm of some sort. About 3 cm (~ 1 inch) long and only 1 mm wide. It is definitely pushing sand up from below. So mystery half solved. It's a worm shaped something, not a shrimp of any kind. For more than that I'd have to catch it and get it under the microscope. Don't think that's gonna happen since I've siphoned the mounds and not siphoned up the critter. Still it's a pretty cool hitchhiker, not something you see every day.

 

[reef lover]

Peanut worm maybe...

 

[OneReef]

Kinda unrelated , but interesting as a mystery I had once. I had a frag on a very small rock on the sand, that kept moving around my tank every night. I couldn’t figure out how this thing was moving about. After a couple of nights of watching with a flashlight, I found some kind of hitchhiker strawberry crab moving the frag rock around for some reason. Always interesting to see these mystery’s pop up...