Predator tanks can be a pain because most predatory fish get large. What about a semi-predatory Hawaiian biotope?:
x1 Centropyge potteri (Russet/Potter's angel)
x1 Canthigaster jactator (Whitespotted puffer)
x1 Zebrasoma flavescens (Yellow tang) - It's a classic.
x1 Cirrhitops fasciatus(Redbarred hawkfish)
x1.3 Cirrhilabrus jordani (Flame wrasse)
x1 Rhinecanthus aculeatus (Picasso trigger) or Rhinecanthus lunula (Halfmoon trigger) - Both classic.