I'm a little late on this but I tube regularly in PA.
You need a TWO bladder float tube with a backrest counting as a second air bladder. You MUST wear a PFD with CO2 types like SOS Suspenders or an SOS waist belt PFD being fine. NO mechanical propulsion is permitted so it's ALL flippers or paddles. (I actually had a Waterways Conservation Officer once ask me why I didn't have a motor on mine and then insist I was wrong when I told him it was against the law. )
No permit or registration is required on PFBC lakes or DCNR lakes in PA State Parks although those rules are don't apply to county or township parks with lakes. In those situations a county or township can prohibit float tube use on their property so it's always best to identify ownership of a lake or pond before assuming it's OK to tube there.
Have fun!