Hate to be the bearer of bad news but...Some of what I would consider the most accomplished fish keepers in the world have failed at keeping them alive for more than a few months. I've had trouble with them as well, on more than one occasion.
They start out healthy and seem to be eating, only to slowly waste away months later. All water conditions and foods have been tried to no avail.
Don't let me discourage you. Who knows, you could be the one who figures it out. email Pete from "That Fish Place".
petemange54@aol.com put the word PAYPAL in the subject line. He normally deletes emails that don't have that in there. LOL. He has them on a regular basis, and ships out every Wed.
FYI, havn't seen her in a wile but that store is the LFS that prettypleco shops at all the time. Pete is the owner, and a heck of a guy.