Mystery knocking solved!!!
 

I was trying to watch a movie when this annoying sound kept bothering me. First I thought something on the aquarium was leaking because it was sounding so consistent. I had to go investigate and this is what I found!!!

Sorry about the bad lighting as only the actnic lights are on

http://youtu.be/k-cPC_g2XcE

So, what is it, a hermit ?

Yeah that get annoying fast

I have two tortises that are in one tank with a partition and the same thin happenes. Bouncing there shells off the glass

It is called knocking crab.:lol:

Yeah its a hermit. I guess he couldn't get traction because there is no sand there only bare bottom where the power head stirs up that corner. Hopefully he stays away from it from now on.

Maybe he was trying to tell you FEED ME :wink:

He is testing out the glass.