I found five of these alive in my quarantine tank AFTER two weekly treatments of praziquantel (Prazipro) at prescribed concentration (2.5 mg/l). All five are/were free living and very active on glass bottom substrate, maximum length ~8mm, round not flat in cross section, no eye spots, no antennae or other projections of head, ventrally facing small round mouth, body surface is covered with white spots and three larger pairs of white patches, one largest pair on head and two smaller pairs on body, the anterior 1/3 of the body is narrower than the posterior 2/3, no internal organs visible except the posterior 2/3 is darker beneath the white spots and turds may be visible near the anus, trident tail end. Their head pokes around a lot, mouthing the glass or very occasionally rising up just long enough to expose the mouth. They are suprisingly fast moving. What are they? Could they be harmful to fish, corals, clams, snails, macroalgae, or anything else I have in my DT? I've got a fish in the QT that I'm afraid to move to the DT until I get this figured out. Please advise if you can. Thanks in advance.