Would a large anemone and one clown be ok in a 6 gal nano?
Depends on size of anemone it can work, bigger question is what kind of light do you have , is it enough to keep anemone alive? What you going to do for flow, what is your plan for filtration? In such a small tank, parameters change rapidly , salinity can spike up if not topped off regularly, temperature will fluctuate, very easy to overfeed and get you nutrients high, where algae will grow. What is your experience in keeping saltwater tanks? If this is your first tank, I would not recommend it starting this small. But it is possible, I keep 12 gal. with 3 fish, couple of crabs and snails, full of NPS corals that need to be feed every day . I keep changing 5 gal. every weekend, running skimmer and big filter relative to size of my tank. But I have a lot of experience, and can see if things are out of wack, and I know how to react and what to do. In such a small tank margin of error is very small, and it can cost fish or/ and corals lives in a matter of hours.