All i can say is good luck..
I hear so many failed attempts with this fish than i do success stories..
Get some nems ,,i hear they eat them up..
One of the few stories i heard about someone keeping one for years was a guy constantly getting anemones for it to eat ..Which kind ,,i can't remember for sure
Can you order sponges online? Specifically just for feeding?
They need sponge meat in their diet. Buying sponges to feed can get pretty expensive; but if you can find foods like this (and similar) that contain sponge, it will prolong his life. Live blackworms are another favorite food. Also, talk to Paul_B and build a feeding station for your Idol like the one here.