I have a 20ish gallon above tank refusium with a sand bed and caulerpa. It empties into a 60 gallon heavy bioload tank. I will post pictures when I re-figure out how to get back on photobucket. Anyway, my refusium has tons of copepods, amphipods, various worms and snails etc. I have always been concerned about the number of red/rust colored flat worms that I get. I never see them in my show tank due to several types of wrasses I think. I was going to treat with flatworm exit as I have done before, but was hesitant as I noticed shriveled up bristle worms last time I used it ( I followed a hobbyists advice and used a heavier dose to kill them all). So I was afraid about killing more than flat worms. I recently heard about the nudibranch that was known to eat flatworms so I purchased one at a local Portland store. He/she immediately moved along the front glass slurping up flatworms. I was curious to see the rate of consumption to see if it would run out of food or if it needed something more than the particular type of flatworm in my system. It has been a week and the nudibranch is quite fat there are still plenty of flatworms for food. It has to work for them throughout the caulerpa. It seems to stop eating and rest periodically whether light cycle or dark. I thought this info might be interesting