well its not pratical for the lfs owner to be keeping a suitibly sized tank just for it is it?
i know its cruel agree 100% but fish are only usually there for days and in a bigger tank they are harder to capture for when they are sold
read the thread
its all in their
we came to the conclusion the only was to get rid of them is starvation, remove polyps and wait basicly
i am honestly surprized the wrasse ate a spider int he first place tbh, but go get a coffee and get reading everything you need to know about them is in there
the fact you even found 1 makes it a extreamly high possibility that there are many more
if i were you i would ditch the frag and do not stock any zoas for at least the next 4 months, this will let the beasts have enough time for a full life cycle therefore starving the spiders
seriously...