It's great that you seem to be having luck with your clowns. But we need to take a closer look at the article.
That's not entirely the true story here though. If you read closer, you will notice that the researchers prepared an EXTRACT from mertens and gigantea. The former was killed in this process (held in methanol for 5 days) and the later was stressed significantly forcing a severe reaction producing nematocytes (3x dipped in iced DI fresh water for 15 min). Both extracts were tested refined and tested crude, or with methanol, dichloromethane, ethanol, butanol and acetone. Yes, filtered, centrifuged, and testing in sterile environments, but they also did not report testing control samples of the chemicals alone without the "essence of anemone". Nothing was tested in a saltwater environment with live animals.
What I read from this article is not that an anemone could be a natural antibiotic or antifungal, but that when extracted, filtered, and processed, there could be some slight antibacterial and antifungal properties to some strains in the laboratory setting. I think you might be drawing desired conclusions from only partial stories. While I can see how you may want to reach said conclusions from this article - and on the surface it seems promising - I fail to see the direct cause/effect relationship from this research you do.