AP,
Chara is really difficult to control. I remove it periodically with a weed rake. It spreads by fragmentation and loves well water! It looks like a vascular plant but is really a form of algae. However it does produce oxygen and it absorbs nutrients. It also make it more likely your pond will be crystal clear as it not only absorbs nutrients it keeps the pond from being stirred up as it is so dense.
I found if you don't have Chara you can have filamentous algae so it's a lesser of two evils. Alledgedly I can use copper products on it because my water is so hard and it won't hurt the trout, but I don't want to take the chance. I've found the copper products are not that effective in my hardwater anyway. Even the chelated copper like Cutrine plus.
Here's wheelbarrow full I raked out of a pond:
