Hi, after several years of reefing it looks like i have somehow introduced some flatworms into my tank and would appreciate help in identifying these and whether they are harmful or if i can just let them get to a balanced population and not worry. I really don't want to add chemicals if i don't have to. Siphoned out a bunch a few minutes ago. Size ranges from less than 2mm to about 6mm (1/4") and color ranges from pale bownish-red to grayish-clear.