Since it's a blue tank, it's best when it's a coral that reacts to it. Since it is an anemone build.. the high end ones like Sherman or Black Widows is what I would to (if you like the red colored ones). Chicago (more yellow) or Colorado (more orange) depending on color preference.
Do NOT mix anemones that are high end because of the low success rate. It's probably expert level (and I've lost so many anemones thinking I can pull it off). You can mix rainbow bubble tip anemones as many as you like.
There are also rock flower anemones, haddoni (which is nice if it a red one that fills the entire tank with a bunch of clowns-- probably not for 9 gallons but for 20-40 gallon tanks).
For my tank, I plan to get inverts instead of fish like pom pom crabs, sexy shrimp (which are fun to watch when they are on an anemone), porcelain anemone crab which keeps anemones in place. I cant seem to find a fish small enough for the 8g.