Drilling holes in the tops would work, just make sure they are small enough so fish cant jump through them.
Damsels get a bad rap but ime yellow tailed damsels are pretty laid back, my clowns are meaner than they are. Yellow tailed damsels are the only ones ive had though so cant say much about others.
Done! just did a bunch not really in any order

Even drilled a whole for my Hydor!

