"HELP" Rapid tapping noise freaking fish out

[salty210]

Hi; I am hearing a strange knocking noise coming from inside tank. Have turned off all pumps and I still hear it. It sounds like tapping your finger on a table. Sometimes its only a couple of knocks and sometimes its up to 7 or 8 rapid knocks. No specific time when it happens, lights on ,lights off, feeding time, or when ever. It drives me and my fish crazy. Any ideas what it could be.

210 gallon aga
50 gal sump
vertex 250 skimmer
200lbs live rock
4" sand bed
8" blue face angel had for 6 years
5" powder blue tang
4" blue cheek trigger
7" foxface rabbit
4"threadfin butterfly
coral beauty
7 green cromis
cleaner wrasse
long spine urchin
sand starfish
40-50 hermit crabs some quite large
30 or so snails

[Leah]

I have it too! I thought mantis but have never seen it, then I thought pistol still have not seen it. I also have a small gobie in the tank and he is still in there. But I do have a foxface and wonder sometimes if it is not him. Who knows I sure can't figure it out either.

[salty210]

Hi Leah I dont think it is the foxface, I can usually tell where the noise comes from and he is not in that area when it happens.

[Leah]

Mantis or Pistol then, have you lost fish?

[salty210]

No, lost nothing, I have seen a lot of videos on mantis shrimp attacks and the knocking in the video doesn't seem to be as rapid as the knocking Im getting.

[Leah]

They say three in a row is probably a Mantis, mine is sporadic not always in a row sometimes only one

[hillbillyreefer]

Snails get stuck between my power heads and the glass all the time. It makes a most annoying clicking rattling noise.

[Leah]

Yeah I know that noise to, but this is different

[salty210]

Yeah I know that sound.I fixed that problem already

[simplycoral]

Same thing happening in my tank!

Haven't figured it out yet

Fish are freaking out when it happens but no fish losses yet.

Simon.