clowns are known for odd behaviors, especially ones that are attempting to go through the process of finding a home for themselves within your tank. If an anemone is not present, they will go through a number of stages in order to try to find a suitable home, more often than not the first of this being the sandbed, they will lay sideways and slowly move the sand as yours is doing, almost creating a little bed for them to sleep in. mine has done this in the past, then they will go through your different corals to see if any of them are suitable. for instance mine tried to host a red monti for a while which was actually kind of funny to watch but didnt not work too well haha. and now they have both moved in with my duncans colony, which i actually love because it really looks great with them in my large duncans colony, and even the duncan has gotten used to them and no longer closes when they are present.