Why is my poor urchin bald?

[BrettDS]

I've had a number of these black urchins in my tank since I was set up 2.5 years ago. They came on my TBS live rock. For some reason, though, a few of them have lost a few of their spines and one of them is nearly completely bald.

I had an issue once about 1.5 or two years ago when I tried to use algaefix to remove some green hair algae. After I had been dosing the algaefix for a couple of weeks I noticed that the urchins started losing their spines and I even lost one or two of them. I stopped dosing the algaefix and the urchins recovered and regrew their spines.

But close to year ago some of them started losing spines again and this one has been pretty much bald. I hadn't dosed any more algaefix or any other chemicals and I figured that they would eventually recover, but it's been a while now and they still don't seem to have all their spines back. They seem healthy otherwise and I haven't lost any, but I don't know what's going on with them.

I did introduce a sargasm trigger and a blue spot toby puffer at about the same time I noticed them starting to lose their spines, and I wonder if one of them is eating them, but in the 10 or 11 months I've had those fish I have not once seen them show any interest in the urchins, much less try to pick at them.

Any ideas about what's going on with the urchins?

 

[Valentini89]

I've had a number of these black urchins in my tank since I was set up 2.5 years ago. They came on my TBS live rock. For some reason, though, a few of them have lost a few of their spines and one of them is nearly completely bald.

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My first question was going to be "any puffers" then I read that you have a Toby. I have 2 tobys in my 26g and don't keep inverts because of them. Most likely something was eating them.


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I had an issue once about 1.5 or two years ago when I tried to use algaefix to remove some green hair algae. After I had been dosing the algaefix for a couple of weeks I noticed that the urchins started losing their spines and I even lost one or two of them. I stopped dosing the algaefix and the urchins recovered and regrew their spines.

But close to year ago some of them started losing spines again and this one has been pretty much bald. I hadn't dosed any more algaefix or any other chemicals and I figured that they would eventually recover, but it's been a while now and they still don't seem to have all their spines back. They seem healthy otherwise and I haven't lost any, but I don't know what's going on with them.

I did introduce a sargasm trigger and a blue spot toby puffer at about the same time I noticed them starting to lose their spines, and I wonder if one of them is eating them, but in the 10 or 11 months I've had those fish I have not once seen them show any interest in the urchins, much less try to pick at them.

Any ideas about what's going on with the urchins?