Unfortunately this guy did not make it. Went under the sand to molt and never came back up. They get very sensitive when molting. I hadnt seen him for 2 weeks (bad sign) so I dug up the sand (by hand which was quite frightening!) and there was nothing to be found. Bodies dont last long submerged in live sand with lots of cleaners snails etc living in it.
If I find another one some day maybe ill try again but this time do a mantis only tank and omit the coral and all the headaches it causes.