I am not sure. Maybe
@ISpeakForTheSeas or
@Jay Hemdal would know?
The Crinoid Squat Lobsters commonly found in the hobby are
Allogalathea sp./spp. (there are currently four recognized species in the genus, but they were only fairly recently distinguished as separate species using DNA).
By all accounts that I've heard, they are very short-lived unless you can keep crinoids to host them - I've only heard of one person somewhat successfully keeping crinoids and trying to keep these (very, very few people are able to keep crinoids with any level of success); the last I'd heard, they'd kept their Crinoid Squat Lobsters for like 10 months (I didn't hear any updates beyond that).
They reportedly (mostly reported by companies selling them and people referencing those companies as sources of info about them) adapt well to aquarium life and take meaty feeds readily, but given that they're thought to feed on the tiny planktonic foods that come by their host crinoid, and given that they reportedly live rather short times in aquariums under normal circumstances, I'd assume they may actually either need the food found by wild crinoids, or that they need the crinoid itself for some reason (physical or psychological).
So, I would assume they would "survive" for a time without a crinoid (similar to how biofilm-feeding starfish survive in our tanks), but likely not thrive - I would personally also assume they need a healthy crinoid host to be able to keep them long-term.
Regardless of it it's actually necessary or not, though, any time there's a strong commensal relationship like this, I'd personally suggest keeping that bond in tact if at all possible; so, given the difficulty of keeping crinoids at this point, I wouldn't suggest keeping one of these.
https://www.reef2reef.com/threads/crinoid-squat-lobster-anyone-have-one.435200/
