Leave it to me to disagree with the common thought....
Captive bred bubble tip anemones and certain non-clownfish-hosting anemones can be kept in tanks as small as twenty gallons. Captive bred bubble tips make a fantastic addition to most reef tanks; they don't usually move much, and they do not harm soft corals in my experience. Hard corals can be damaged somewhat in my experience, though, but if they anemone is well-fed, they typically stay put.
Run regularly changed carbon in the filter to remove allelopathic toxins before adding an anemone to a tank with other cnidarians.
Finally, while there are some very pretty corals out there, few in my opinion match a well cared for anemone. If all their necessities are provided (lighting, flow) captive bred bubble tips are a breeze to keep. Check out Karensroseanemones.com if interested.
P.S.
gain experience with some corals first to avoid losses and "get the hang of it".
