Consider the neon blue gobies. A mated pair or single is interesting and colorful. They won't control whitespot either, but IMO
would do fish cleaning chores (dead skin, maybe fungal growth, and stuff) like cleaner wrasses. Seems that the cleaner wrasses are abundant, but I remember Robert Fenner suggesting that hobbyists don't buy'm, to convince those that harvest to keep'm in the ocean where they serve fish in natural reef communities well. Haven't heard that much since the book, so don't know if it's a huge concern. I still like the neon blue gobies better anyway.