I have these weeds/alge in my pond. Most of it is growing up from the bottom in the shallow areas. Some of it is floating. Can anybody give me an idea what it is and how to get rid of it? Also, I irrigate my grass out of this pond. If I put something in the pond to kill the unwanted plants I want to make sure that it's not something that will kill my grass. Any help would be greatly appreciated. Thanks!!