I had to reply after reading your post, I have just gone the war with the "flat worms" and hopefully won the battle.I absolutely hated those things, they took over my tank also, it was so bad that i had purple live rock and you couldnt even tell, also if you have noticed if you get one on you and smear it accidentaly, it leaves a groce smell behind.They even started to hang to the glass,and also was covering my sand and gravel,im talking 1000s of them and that was the last straw.I tried all the home remedys first...1st i tried the wrasse familys, bought every type of wrasse i could find, because some wrasses supposedly eat them, but i never found one that did.... 2nd was the syphon treatment,i syphoned every day to find that it seemed the more i syphoned the next day there front lines were busting through with more and more troops, so i gave up on that.....between the syphoning and wrasses( i tried the wrasses for 6 weeks then gave up)I had to resort to a more heavy hitting solution.By this time, they had completely covered all my rock, i was bummed, and felt like i was being invaded and just couldnt take it anymore, I Hated Those Things..so i called Big Als and xplained to them my situation, first thing they told me was to try the wrasses...needless to say we moved on to the next step.They suggested i buy some "Cupramine"from seachem, its copper and i had to take out my plants and such(in a safe tank),leaving just the fish, which is only a few(wrassses hehe)and my live rock..my tank had only been established for about 5 months so thank goodness it was easy for me to do than one that had been set up for a long time. I have about 200 pounds of live rock in a 85 gallon tank but my live rock was soon to be dead at least till my water turns around back to normal, i live in a small home and have no place to transfer the rock and also wanted this to be a one time event, knowing now is all it takes is one for the battle to start all over again.I would say that if all else fails, this treatment worked for me within hours,BUT WORDS OF WARNING-after going this route, be home and prepared to start syphoning soon after the treatment, these critters started floating everywere in the tank and the SMELL from them is absolutlely horrible after death, it actually stunk up my whole living room for 2 days afterward..But the ends results to me was worth it,i am now worm free and plan to stay that way, I only can come up with one thought to were they came from, and that was a lfs i had bought some rock from them and soon after i noticed them, i had a smaller tank before this one for 2 years and never had a problem at all, and used most of the same live rock.I am now going thru water changes and running my filter system with just carbon filters,and pumping in the vitamins for my live rock, my water levels are coming around great and my copper test showed only 01-02ppm and my live rock is coming back to life. When i get to 0ppm im going to try one of my hardy plants and see what happens, by the way, i didnt lose any fish during this, they took it like champs...after all this, id just like someone to "tell" me were these things come from and originate from, it seems like with all these posts, more people would have gone thru this but it seems isolated...thats about it, hope i helped in some way and good luck