What Cory said, only I wouldn't even bother with a Manderin until you hit six months at the least to guaruntee a pod that will sustain a manderin.

Chances are that you already have some pods and copes in there. But the fuge, with the macro, has a tendency to provide some of the smaller bugs to the display tank. A pile of rubble will provide an area where the bugs can knock ankles and stay safe (relatively safe) from a searching manderin.

Were you truly insistant that you try your hand at a manderin, I'd suggest a target manderin as they can be "trained" to eat prepared food. i've only heard a tale or two of someone happening onto a physchodelic that eats prepared food.

I had a scooter blenny and a target, and for about six months they got along. But at some point I think the target realized it was competing for a dwindling supply of food with the scooter. At that point the target wouldn't let the scooter anywhere near the rock work. I eventually lost the scooter as neither fish ever ate anything I put into the tank.

As far as macro with bugs, I've got some if you have a need.