^ That. You need some dither fish --- middle swimmers that will reassure your skiddish clowns that all is well and it is safe to come out. I have assorted rainbows in with mine.
The other thing you can do that helps, clowns should really be fed 3 times a day in small amounts. Not only is this beneficial for their health, but it also helps them associate you with food. And food is good. So you must be good to, right? You want your clowns to see you and think "o hes here to feed us, lets dance!"