Publix sells a medly of frozen fish that has squid, octopus, cuttlefish, shrimp and mussels. Pick out the mussels and toss them (for some reason, those are cooked; the rest of the stuff is raw). I spread it all out on a cutting board, chop it into small, bite-sized pieces, refreeze it on a cookie sheet and then store it in a Ziplock bag in the freezer.
My GDM also eats krill and silversides (from the LFS) and raw tableshrimp (from Kroger, when it's on sale).
Mine for some reason didn't eat for several weeks, but once he started he became an excellent eater. I feed him every 5-7 days, depending upon when he comes out of his cave and lets me know he wants a meal, and I feed him until he's sated. I wouldn't feed him any more often then that, since these fish can experience problems if overfed.
Since yours is in a small tank with small fish and inverts, I'd definitely make sure he doesn't miss meals. I would never say an eel absolutely, positively would not take an opportunistic bite if they get hungry enough. My GDM is housed in a 90g and my smaller fish have sleeping quarters on the opposite side of the display. That won't be as easy in a 29g.
Good luck with your little guy. I love mine.
