I would take the "happy" with a grain of salt. My percula pairs are fore sure much more excited since they have their anemones.
At a bare minimum Anemonefish seed a suitable replacement, or they don't behave naturally and just swim all day restless around as if they are looking for something (which they actually do: an anemone).
Some will take on leathery or stony corals or even polyp colonies. Though the best anemone substitute is simply a plain red ceramic flowerpot of suitable size. I can't remember any of my past or present ocellaris or percula to reject one.