I had the same problem, bought a LMB. He wouldn't eat frozen, barely touched the flake, and wasted away, even after I moved him to my QT which was full of hair algae.
For that reason, I can't recommend getting a LMB, unless you can get it to eat something else besides algae. Its not worth seeing a great, personable fish waste away.
I have had good luck with the astraea/turbo snails from SWF mowing down hair algae. They eat it all, except for one strain in my 12g, that they won't touch.