It sounds like filamentous algae. Very common problem for pond owners. There are a few ways to get rid of it. I've read a lot on here about a chemical called Cutrine. There are a lot of posts on this forum about this product that should help you. I've never used cutrine, but I've always used copper sulfate crystals better known as bluestone on algae. This stuff works quick but don't put too much in the pond at one time or it will cut off the oxygen underwater and the fish will die. I had that happen at one of my ponds 3 years ago. After catching fish out of my other ponds and transferring since, I'm now catching big fish.
As far as cattails, it depends on whether you really want them or not. They cn provide structure for bass and make a decent place for fishing. The cattails will die when it turns cold and sometimes won't grow back. Personally, they don't bother me unless they cover the whole pond. I've read that Weedtrine-D, Rodeo, and/or Reward will kill cattails.
Hope this helps
