I've had six clowns for around 5 months now. Got them when they were really quite small and they have grown a little bit. They are shy of humans, dashing for cover whenever someone approaches the tank. I've given them a part hollowed out wooden stump to hide under, but they are not permanently hidden in there.
Whenever the room is not busy they happily roam the entire tank, not intimidated by any other occupants, and irrespective of whether it's day or night and the lights are on or off. At feeding time they readily come out to grab some sinking flakes or even those floating. Again though, any movement outside the tank that they can see sends them scurrying away! They also come and nibble on dried bloodworm tablets, and frozen cubes as well.
The snails bit is interesting. A few weeks ago I bought three average sized snails, and one died fairly quickly of unknown causes. I thought it was the shock. However the other day I noticed a clown trying to nip one of the remaining snails, which quickly withdrew itself. I now wonder if my beloved clowns have a darker side to them!!!
Best of luck....
Irf.