Hi,
I never kept clowns before, but i have kept bifurcus in the past.
I think it would be better if you got a bigger tank for these guys. I kept 2 couples of bifurcus in a tank of 25 gallon and they where very active and busy.
The bifurcus where captive bred, most clowns are not (at least here in Europe) and need more space and rest to acclimate, at least that's my idea.

IPeople keeping these told me that they can be hard to acclimate from time to time and sometimes suddenly die within the first year of keeping them.