Diadema Urchin "Missing"?

mr_noodles · Mar 4, 2020

To begin, tank is healthy and stable. Have various fish, CUC, and corals (softies, LPS/SPS).

Added a Diadema to the tank to assist in turning the sandbed since my snails would only stick the the glass and the hermits would only transit the sandbed to go to the next rock. Boy, did that guy do his job! I had a completely spotless sandbed after 2 days, then on day 3 I never saw him again. I checked everywhere and cannot find him (it's been 3 days since I last sighted him). Before I begin shifting rocks around to find him, is it normal for Diademas to bury into the sandbed? If so, I want to avoid looking for him in the event I squish him with the rock.

Thanks!

Tahoe61 · Mar 4, 2020

It has to be snugged up in the rock work. Urchin can be very nocturnal.
I would be very hesitant to move rock and stress out the entire system.
If the urchin has died there is nothing to do except run some basic chem and a WC If indicated.
If the urchin is crammed in the rock work you can not move it with some injury to the urchin.
Basically nothing gained by moving rocks.

Let us know if he shows up. Look in the tank at night with a flash light.