Yes, but is Warnberg? I have had Valonia and still do, but it never got out of hand. I have maybe 5 - 1/2" silver bubbles. They dont multiply very fast, this tank has been up for a while and I put them in intentionally with a colony of zoas. The originals are gone, but the few that are here have popped up in the last year, on different rocks. I never heard of anyone saying it was bad. Is it and should I take it out? Seems pretty benign. I really dont mess with anything in the tank, but it seems easy to take them out. In the wild they arent covering much either, just one or 2 here and there.