uuuggg I have alot to say lol, alright a black long spine, rock etcher, pincushin, and tuxedo, urchin will all be fine in nitrates up to 40 ppm, anything above that is when spines are gonna drop. rock slate urchins are fine until nitrates hit 28ppm, just to let u kno... but if your nitrates are below 40 they are fine for an urchin to live in, BUt if your nitrates are 10 ppm higher than your lfs the rule for urchins that not many people knwo is for every 5 ppm of difference in nitrates you need to acclimate an hour after the original 2 hours of acclimation, so if the lfs has 0 nitrates and you have 10 ppm nitrates. then you need to acclimate a standard 2 hours for your urchin plus 2 more hourse for the amoutn of time it take your urchin to overcome the difference in the water without causing shock. urchins are incredibley hardy, but they need to be acclimated as if you were acclimating a very difficult addition. urchins will do fine as long as they dont notice any changes in water parameters. next thing. urchins sometimes fall on new glass if it feels different. also if your urchin was knocked around in the bag alot it can mess up its equilibrium for a couple days, leading it to fall. Your urchin I think just wasn't acclimated long enough, sure there are people who acclimate them within an hour and theirs do fine, but most likley the case is that their water parameters are not too different. Make sure your salinity isn't too low, urchins hate the feeling of low salinity, they prefer med-high. if their spines become brittle it's because of low salinity, they can't produce the nutrients neccecary for proper spine growth at low salinity.