After the last Aiptasia disappeared (about 2 months ago), they slowly started to disappear (it's their only food source, sadly). I saw one last week, but they have now pretty much disappeared, along with any trace of Aiptasia. It amazed me how they found it all - I had some in some very difficult-to-access spots on my return plumbing - they got it all.

I don't know how toxic they would be to fish - all of my fish seemed to know that they were to be avoided - I saw my trigger, flame angel and hawkfish all pick up one, and immediately deposit it back where they found it...