I am running a pretty clean system at the moment with pretty high flow and so far after sucking out what I saw in my refugium and dipping the two suspect corals which none come off of I am just going to do the same for now. I don't see anything in the DT yet.I had flatworms in a tank once but they didn’t really cause any issues. I just told myself they were part of the clean up crew. I have seen them reach plague proportions but that was in a tank with pretty high nutrients. Not sure if that correlation is causation.