They are NOT easy to keep long term at all. How long have you had yours Blemmy?
Success beyond a year is not all that common, again, as with many harder echinoderms, due to starvation...I DO NOT recommend trying them. They need room to spread out, are generally nocturnal, and actually require pretty specific particle size food. Most people who have long term success (and again, it is not all that many) have access to lots of invertebrate larvae. This is not a "food in a bottle" creature..but rotifers, brine nauplii, etc. SMALL plankton.
The are definitely not part of the clean up crew, though certainly reef safe!!
These are not an animal to purchase without a great deal of research into care, and preparation for keeping them. Most will die of osmotic and shipping stress (be SURE your tank is mature, and water quality PRISTINE, especially specific gravity). They need a fair amount of food, so water quality could become an issue at some point.
Odds are your $35 purchase will be short lived...I would instead encourage the LFS not to carry them (especially not to carry animals they can't even tell you about). Really, I strongly discourage anyone trying, unless this is a very large mature reef tank with refugium, deep sand bed, etc, etc.