couple things you should know about these fish,
they can get large
they dig tunnels under live rock(live rock should be placed before the sand goes in, so that way when they start to dig, the rocks wont cause a land slide.)
unless hungry, you'll only really see there heads.
i have two that are about a foot long each, had them for about 2 years now. very cool looking fish, and oh if you do purchase one. be prepared for everyone ((EVERYONE)) to call them "eels"....
and for the less minded aquarium people will call them "snake thingies"
if your going reef and would like a couple of colorful fish, i would think about your selection, cause with bigger size comes bigger waste.again these fish do get large over time. im a fan of them, so your call...
hope i helped some, sorry for no pics. maxalmon has a pic of one, heres the link....
https://forums.saltwaterfish.com/t/335216/foamback-project-101