Okay I couldn't find any frozen algae at the local 3 pet store but I bought some algae tablets. I wasn't sure if they would work for my lawnmower blenny until I find some frozen algae.
the LMB is probably not going to have any interest except in what is growing in the tank. some have LMBs that eat flake food, algae, etc, but the I had would eat anything except off the rock and glass.