Look up anchor worms. You didn't say they were on the fish. A close up pic might help with the ID. If you think that's what it is praziquantel or somthing like Prazipro orAPI General Cure will take care of them. It is very diffacult to diagnose from a discription in many cases so a pic is worth a thousand words if its close up and good quality.
That sounds like hydra. Look for pics of it to see if that is what it is. Clean the glass and do a large water change to controll them without meds. The most effect med to use against them is flubendazole but you it only if you must and at the lowest effect dose possibile. Try to controll with out with out it if at all possibile.
