After the tank has been stable for 6 months and you have had the experience of testing on a regular basis and can manage to keep the ph, alk, temp., specific gravity in check and have your water change schedule down to a regular thing once per week, then I would say of the host anemones, only Entacmea quadricolor (BTA) is an option. If you have two ocellaris in there, then no other fish or corals. A BTA will grow large and practically fill a 12 gallon, but can be successfully kept in that size tank with good husbandry.