Pincushion Sea Urchin (Lytechinus Variegatus)

[stanleo]

I got a pincushion sea urchin yesterday. I drip acclimated him for 4 hours and made sure there was nothing in there that he could push over. My nitrates are below 5 ppm so I think that is ok. He seems to be doing fine, everytime I look in the tank he is in a new spot and I don't think he has lost any of his spines. His feelers are always moving so that seems like a good sign.
 
I am just concerned that his spines aren't all fully extended. Is this the stress of the move from the shop to my home or is this an indicator that something is wrong? I read that they need seaweed to supplement their diet of algae and small stuff that they eat on the rocks. How often should I feed that? And while I am asking that, why don't they ever tell you that info when you read the articles?
 
Thanks for any info you might have. Here he is

 

[Donya]

The spine arrangement looks normal to me. How they hold their spines depends largely on flow and whether they've been agitated by something. How often you need to target feed depends on the naturally available food. I feed mine daily in overgrazed tanks. It's best to rotate at least a couple types of seaweed. Usually seaweeds are sold by color rather than species, which isn't entirely helpful, but I rotate red and green species mostly. Things sold as brown seaweed have never been much of a hit with my various urchins.
 
EDIT: oops, forgot one thing.
 

why don't they ever tell you that info when you read the articles?

 
Mostly because they are poorly documented animals, like many invertebrate species in the trade. People also tend to think of grazers (although grazing urchins usually are not strict herbivores) as janitors with the idea that if you feed it, it will become lazy and not clean your tank - which leads to malnourished or starved animals that sometimes behave badly and eat things they aren't supposed to. Of course, grazing urchins can become lazy blobs that just beg for handouts all the time at the surface, but usually they are feeding all day and night on various things, so you really have to add quite a lot of supplements to cause that. One feeding a day is unlikely to cause problems.