I've never had issues with acclimating urchins.
I've even bought rocks with hitchhiking ones (as in, they weren't even submerged, at all) that lasted me for years, knowing what species you were using would help.
I will say acclimating them in the same water as mushroom corals isn't the best idea, especially if the water has a lot of the 'mushroom juice' chemicals in such a small space. In a tank/ocean that stuff gets filtered/diluted but in an acclimation space its a soaking poison chamber.
My acclimation method is float for 30 minutes (15 is too short IMO), and I don't drip, I just dump some of the water out, and scoop a little water, pour more out, scoop, pour, scoop, pour, etc until pretty sure at some point the water is 100% rotated with my tank.
A lot of the urchins we get in this hobby very frequently get trapped in tide pools, so I'm not 100% sold on them being that sensitive (otherwise the water in the tide pool evaporating (salinity spikes) then suddenly being reunited with the ocean would all get shocked and die) and even if they are its a slow reversible process (spine loss usually).
My only assumptions for OP is bad supplier (condition they were in prior to shipment) or possible poisoning from long acclimations. The most recent one sounds like its best to give it time, lethargic behavior and spike loss for a new urchin is normal, they're stressed and they shed and regrow spines all the time.
I've even bought rocks with hitchhiking ones (as in, they weren't even submerged, at all) that lasted me for years, knowing what species you were using would help.
I will say acclimating them in the same water as mushroom corals isn't the best idea, especially if the water has a lot of the 'mushroom juice' chemicals in such a small space. In a tank/ocean that stuff gets filtered/diluted but in an acclimation space its a soaking poison chamber.
My acclimation method is float for 30 minutes (15 is too short IMO), and I don't drip, I just dump some of the water out, and scoop a little water, pour more out, scoop, pour, scoop, pour, etc until pretty sure at some point the water is 100% rotated with my tank.
A lot of the urchins we get in this hobby very frequently get trapped in tide pools, so I'm not 100% sold on them being that sensitive (otherwise the water in the tide pool evaporating (salinity spikes) then suddenly being reunited with the ocean would all get shocked and die) and even if they are its a slow reversible process (spine loss usually).
My only assumptions for OP is bad supplier (condition they were in prior to shipment) or possible poisoning from long acclimations. The most recent one sounds like its best to give it time, lethargic behavior and spike loss for a new urchin is normal, they're stressed and they shed and regrow spines all the time.
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