Long spine urchin spines

[Reefman29]

Hi all, I have a black long spine urchin in my reef tank and it has lost its long spines and now has significantly shorter spines. When I say lost, this has happened overtime and the spines did not suddenly all fall off at once as happens when urchins are stressed/ about to die. I wanted to know if this has happened to others and if anyone knows about possible causes.
Thanks, Ryan

 

[Betta132]

Tank age?
Time you've had the urchin?
Tankmates? In particular, anything with a beak?
Is it even or spotty?
Pics?
Could a pump or similar somehow have trimmed them down?
Do you possibly have hitchhiker crabs?

 

[Reefman29]

Tank is 6 years old. The urchin has been in it for at least 3 years. 2 clowns, 1 white cheek tang, 1 pj Cardinal, 1 mandarin- nothing with beaks. All the spines are approximately the same length, urchin appears "normal" moves actively, active tube feet, no discoloration. 2 koralia power heads so it would be difficult for all of them to have been cut at the same length- they appear rounded and natural looking. I haven't noticed any hitch hikers, but how big would they be? If they are small then I did not notice

 

[Betta132]

Could he possibly have somehow worn them down, maybe gradually broken them off on things? Or have there not been any broken spines at all?
Any idea what the calcium content of your water is? Do other inverts do well? If not, I'd think maybe they spines are gradually breaking down from lack of calcium in the water.

 

[ThRoewer]

What type of rocks do you have? In my experience, diadema urchins need calcareous rock to graze on. Ceramic or other not calcium based rock may not work for them. This is because they don't just scrape the algae off the rocks, but rather remove a thin layer of the rocks that contains algae as well. I think they get at least a part of the calcium that they need for their skeletons from this source.
Another thing that is likely important is to keep Alk and Ca levels in the water at the right levels.

I tried keeping 2 diademas in a tank with Real Reef Rock (to my knowledge largely made of ceramic), and despite plenty of algae they perished rather quickly.
I tried it again, this time for algae control in a tank I cured live rocks in, and those 2 are still with me, over a year later. They have since moved twice and are now in the sump of my 200 gallon system.

Sent from my XT1254 using Tapatalk

 

[Reefman29]

It is possible they gradually broke off. The spines it currently has make him look more like a pink pincushion type of urchin. Calcium is always around 420 PPM with minimal change. Other inverts are doing well - usual collection of hermits, snails, mix of corals. The rock is mix of BRS reef saver rock and a large piece of unknown origin. The alkalinity and calcium were not always exact in the past, within the last few months become more keen on checking them weekly and ensuring the levels are correct. The urchin has been in the tank for a few years so it definitely endured the levels being low and some swings

 

[LadAShark]

Perhaps, if consuming calcium from rocks is the problem, you could get some calcrate pills and wrap them in algae (that they would eat) and try that. That might help keep him without having to change too much in the tank.