In nature, often several clowns will live in one anemone. There is the dominant female and her mate and then several intermediate males that remain smaller and, in effect, are in wait for the mated male to get knocked off so they can assume the position of the paired male. So, if you get 4 or 6 small ocellaris, it is possible that a dominant pair will emerge and then the smaller males will be further down on the pecking order. The natural hosts for ocellaris (H. magnfica, S. gigantea) are not beginners' anemones and are considered difficult to be kept in aquariums. On the other hand, ocellaris usually take to Entacmea quadricolor (BTA), which is the easiest of the host anemones to keep. If you can get a captive-raised anemone (clone) and tank-bred ocellaris, you will have about as bullet- proof anemone/clown association as is possible. For a beginner to anemones, I would encourage you to get all tank raised stock. It will make for a more enjoyable experience for you. Wild caught ocellaris commonly have parasites and arrive in weakened condition. Not to mention the fact that, the tank-bred ocellaris are often selectively bred for brighter/prettier colors.
A BTA will not outgrow a 100g tank. However, BTA's will often clone. And, if you get a cloned one to begin with, then odds are, it will certainly clown once it becomes large.
