gaijin wrote:
My tank is several years old and I haven't added anything new in well
over a year. Today when I got home there was a large mass of what
looked like tangled string attached to a rock. The mass is about the
size of my fist and there was no sign of it yesterday. I grabbed some
of it and it breaks apart fairly easily so it is rather soft.

Anyone have any ideas as to what it could be?

When it comes back take a pic and post it so we can take a look at it.
Thanks