hi, if it dies of ich, would advice to quarantine them first before introducing to main display tank. This way, you can feed it and observe that it is well free of ich or other diseases. Then when introducing to main tank, better to put in a large submerge container, preferably those acrylic ones with holes. then its fellow tank mates can 'introduce' themselves.
dogface always eats mostly anything. likes mussels. also, it likes to have a nice hiding spot where it can feel safe.