Well dont worry about the flat worms...
I say this because of my own experience, I have a 29 gal reef with a 30 gal fuge with Thousands upon thousands of flat worms in the fuge. however i do not have them in my reef cause of my hungry mandarin (who is fat and happy) and my hungry sixline wrasse.
Also no worries to keep the sixline alive, mine eats cyclopsease (sp) brine, krill, squid, and mysis.
but those two fish keep the extra critters to a minimum in the reef
oh and by the way i have the red ones and some white ones.
just my own experience and input