Hi I'm very new to this, my grandfather passed away and now I take care of the pond. I am actually really starting to enjoy it, however I am pretty much clueless about alot of it. There are these big thick string like things I pulled out and have no idea what they are and if i should take the rest of it out. Does anyone have any idea what these are? I am in northern california, bay area. The first 2 pictures below are of the acutal stuff the 3rd is the pond where it came from. Thank you.