If your tank is big enough, you want a Goat Fish.
http://www.wetwebmedia.com/Goatfshart.htm
I read your note because I was also doing some research on my situation:
I have HUGE Yellow watchman goby, or at least the biggest I have ever seen. My options are to place him in either:
A) 90gallon reef tank where my two yellowheaded jawfish are the priority to stay healhty and relaxed. I'm thinking there's plenty of potential to have bottom battles and one of the jawfish could likely be fully swallowed by the goby.
B) 200gallon FOWLR with 26" Snowflake Moray Eel, Tuskfish, Foxface, Yellow Tang, Angel to be determined, possibly a Picasso Trigger. My concern is being chased and killed by the Tuskfish and/or the Trigger. I don't think the Eel would catch it, but I can foresee the goby committing hari kari and trying to jump out at the sight of the eel.
Thoughts?