If it were me, I'd put the checkerboard in as the one fish in the tank. I know it sounds mean but, well if the velvet isn't gone you'll know, and if it is gone, your checkerboard will have some time to heal up and de-stress before you put the other fish in the tank?
I hope this doesn't sound too brutal but it makes sense to me if its not going to fare well as it is
Alternatively, I guess that may leave you with a checkerboard wrasse that dies of marine velvet and then you have to wait another 8 weeks. Although I would imagine that if you're that close to 8 weeks you're likely safe.
Ugh, I haven't helped at all have I?
