You already have a watcher goby. Mine does clean the sand for me. You have a small tank, so I would not add any more sand cleaners to your tank. I would hate to see them starve to death.
I think a rainfords goby would surely starve in a 18. They prefer sandbed fauna and can be difficult to get to eat anything else. I know from experience. Plus like mwrager said you have a watchman.
exsacataly reepher. I just try not to make it a habit to dish out "ABSOLUTE" advice, you never know, he could have a 100G fuge attached to it and I could be a monkey for not knowing it.
Say is that hat photoshopped on there?