I had two problems, apistas which came on some live rock and flat worms. The apista was eliminated by taking the live rock out and leaving it in the sun for a couple weeks. This may be a problem for some...but it worked for me.
The flat worms would hang out 95% of the time on a my hairy mushrooms which are mounted to a small rock. Once a week I would remove the rock and dip into R/O water for 1 minute...shake the dead off and return it to the tank. The remaining worms in the tank would go to the mushrooms again and after 3 times they are all gone!
The flat worms would hang out 95% of the time on a my hairy mushrooms which are mounted to a small rock. Once a week I would remove the rock and dip into R/O water for 1 minute...shake the dead off and return it to the tank. The remaining worms in the tank would go to the mushrooms again and after 3 times they are all gone!