what is it attached to, you maybe able to pull what ever it is attached to out and clean it with tap water.
I'm fighting a little bit of it myself in my 100 gallon tank, didn't have this issue untill I started using easy green from co-op.....that want happen again. I hate any of the ideas they say to use to get rid of Stag, none of them are really safe and can cause more harm than good if not done right.
I do know I will not use the Peroxide treatment, I have fish that will be like, oh cooool look at the bubbles lest go chase them......
Good luck....