Mine loves mastick. Also live blackworms helped when new. Now he will eat mastick and most frozen as well as clams and muscles. Will not touch pellet or flake but I only use those as treats. I mostly feed PE mysis and a homemade seafood mash.
I did observation only QT and had rock in the tank rather than the sterile bright white pvc. I've read of too many dieing in QT is why I did it this way.
I have one of these feeders. He sees me walking to the tank with it and comes begging. His tank mates, a yellow tang and flame angel hang out and eats his scraps from the feeder. They get fed also tho.
The one you received looks good.
https://www.reef2reef.com/threads/copperband-butterfly-cbb-feeder.942707/