Here is some info from our friend Mr. Fenner. Joe this diddy about selection and collection maybe something that you ahve run into with your inability to keep them.
"The single most important 'tip' on picking Grammas I can grant you is to be patient; wait a good week or two after your supplier receives theirs to purchase them.
Freshly imported caught specimens way too often suffer from post-decompression stress... and something else; the ill-effects of chemical tranquilizing. Florida outlaws the use of Quinaldine and MS-222 (tricaine) but their use in other capture areas of the Caribbean is pervasive. Though not the scourge of cyanide use, there is decidedly higher mortalities associated with true anesthetic versus 'pure' hand netting.
How to tell which type of capture technique has been used? You can't; just wait for a week or two. Trust me.
Grammas live close by their nooks and crannies, upside down, right side up, at all angles. They prefer as much decor, broken up environment as possible, as well as low illumination.
These fishes make great additions for reef tanks, staying small, not bothering invertebrates, and keeping deviant live rock critters, like benthic crustaceans and worms in population check.
Grammatids make great bioassay organisms for an individual system or store on mixed tank recirculation. Talk about "a canary in a cave"; their color and behavior fades with diminishing water quality. Water changing, reducing organic loads, re-elevating pH can be physically correlated with their observable health."