i have just got home and noticed little white things on the glass of my tank in side and on closer inspection with a magnifying glass they are moving i have had a quick look on google and think it could be planaria how worried should i be how should i treat it and are they dangerous to my oscars or could it be something else

Yes, you are correct, they are Planerian. I shouldn't worry, they are totally harmless and may cause your fish any problems whatsoever. They are just a little unsightly and normally thrive if you overfeed. I've never had them myself, but if you reduce the amount of food going into the tank and try and remove as many as you can, you may be ale to keep on top of them and eventually rid them from your tank

OFL is right. The cause is often due to overfeeding. Only feed what your oscar will eat in 2 mins (twice a day if less than 6 inches, once a day if bigger than 6 inces). Remove any uneaten food.

Reguarly cleaning and water changes and not overfeeding should eventually get rid of them