Sometimes pictures are hard to use to make a specific identification unless they are taken properly for identification purposes focusisng on specific features of plant parts. I think your pictures, esp the middle one are adequate to say your plant is Chara. IMO the first picture lacks adequate 'leaf' features and close enough detail with too many stems bunched together to make a real 100% positive ID. The third picture looks like a typical Chara growth habit.
Some info about Chara aka musk grass or stonewort. Stonewort probably refers to the sometimes crunchy or crusty feel of the plant due to lime encrustations that form on the plant surfaces. Technically Chara is an alga, but superficially looks like a 'higher' vascular plant similar to Naiad, Coontail, & a few others. Chara tends to prefer harder or more alkaline water compared to its cousin Nitella. Your pond receives well water which is usually high hardness, so your pond is probably infested with Chara, not Nitella. Being an alga, Chara for chemical control needs an algacide instead of a herbicide for Naiad and pondweeds. Chara can be difficult to control chemically.
If the pond is small most of the Chara can be raked out using various 'tools' such as the Lake Rake or homemade rakes or drags. Chara usually regrows fairly quickly depending on when it is removed during its annual life or growing cycle.
Some types of fish such as grass carp (white amur) or tilapia will eat it. Amount of Chara and size of pond will determine how many fish it will take to control the Chara. For ponds less than an acre, I often suggest to use enough fish to just help manage Chara, you remove some, treat some with a granular algacide, and let some grow for habitat.
There is a good amount of discussion here about Chara, some pictures of it, and how to deal with it. A search of this site for Chara or Chara control should yield more information about it. For starters see these:
http://forums.pondboss.com/ubbthreads.php?ubb=showflat&Number=265724#Post265724 http://forums.pondboss.com/ubbthreads.php?ubb=showflat&Number=288470 http://forums.pondboss.com/ubbthreads.php?ubb=showflat&Number=285601http://forums.pondboss.com/ubbthreads.php?ubb=showflat&Number=304637http://forums.pondboss.com/ubbthreads.php?ubb=showflat&Number=33849http://forums.pondboss.com/ubbthreads.php?ubb=showflat&Number=247062http://forums.pondboss.com/ubbthreads.php?ubb=showflat&Number=317850Thread where the first link was located
http://forums.pondboss.com/ubbthreads.php?ubb=showflat&Number=33329
