Short Spined Black Urchin Spines Falling Off

[Timmay]

Hi,

I'm trying to help some friends solve a problem with their 55 gallon reef. They have a small black urchin (around 3" in diameter) that's losing its spines. The urchin is similar to a long spine black urchin, but the spine are slightly thicker and much shorter. Approximately 45% of the spines are gone. The urchin seems to be wedging itself under rocks or is hiding under overhangs. The spines appear to be falling off even when it's not wedging itself in places.

The tank has around 75 lbs of live rock and several healthy soft corals and zoanthids. The pH is 8.4, nitrates/phosphates aren't detectable, sg =1.025, alk =9.0. There's another identical urchin that's not showing any symptoms. Any idea what's going on? Specifically, I need help understanding if the animal is "sick" with something that could make the rest of the tank sick.

I tried to do searches to find more info, but I haven't been able to do a search (unless it's 3:00 am) in months.

Tim

 

[ophiuroid]

Is this a new urchin?

It is not likely that the animal will make the rest of the tank sick. Often these issues are related to water quality problems.

 

[Timmay]

The urchin has been in the tank for several months. We haven't detected any issues with the water. Can you suggest something we should look at outside of what I've already mentioned?

Tim

 

[Timmay]

Also, I forgot to mention that the urchin's remaining spines are "drooping".

Tim

 

[ophiuroid]

Is there still significant algae growth?

 

[Timmay]

There is, but it looks to be mostly filamentous and diatomic. Nothing I would consider out of control. The other urchin seems to be eating whatever it is. He leaves trails of algaeless rock wherever he goes.

 

[dkk08]

will the spines hurt any fishes? Especially those bottom dwellers?

 

[marfuerte]

Take a look at Dr. Ron Shimek's article "Sea Urchins A testy subject" from a couple years ago. Sounds bad from the description--I'd isolate it cuz it sounds like it might not make it.

 

[Tinker]

Not all urchins are algae eaters. I have a little golfball sized urchin with and purple and spines that I learned is a carnivore. It has eats whatever stays still long enough. Kind of a pain but I've had it for a while now. Also, once it starts dropping spines it's pretty much over. I've lost a few urchins and they all go that way.

 

[graveyardworm]

sea urchins a testy subject Happy reading