Urchin died

[jostafew]

I'm sad to say that I recently lost an urchin (and a couple other inverts) after neglecting my params for way too long, just water changes and top offs. As it turned out my SG was down to 1.020/1.021 which was enough to take out the small tuxedo urchin, the two cleaner shrimp, and my two little red starfish. Pretty dissapointed that I let it get that far, but this incident has put me on a new mission with reefing in general so it's not all bad. In the process I discovered that the calibration on my refractometer was a little off too, so that was contributing to the problem as well.

BTW I had a large pincushion urchin that was OK and a Red Fire Shrimpt that seem to have come out unscathed, so it seems that certain species are definetly more tolerant to those water conditions than others.

A couple other things to consider; is there enough algae growth in the tank to support the urchin? My buddy tried tuxedo urchins twice, both times he lost them after a couple months. In his case the calc/mag/alk levels were pretty low, and not much algae growth at the time. Not sure if those params being low was ultimately whey he lost the urchins, but he has not been successfull with them.

One last comment, I doubt it was the crab that did in your urchin, probably just there for dinner after it had died.