Answer: I don't know of anything you can spray that would kill the cattails without killing your fish, and any other vegetation in the area. Besides, your state may have strict regulations on what you can use in a wetlands area. I would contact your state's Department of Natural Resources. They will have information regarding your state's regulations, and may even have some advice.<br><br>The filling in of wetlands is a natural process called eutrophication, and the only way to change this is to either connect the pond to a naturally occuring stream that introduces fresh water (this type of activity is also probably regulated) or dredge the bottom. I suppose that if you were to manually harvest the cattails, you might weaken the plants to the point that they don't encroach any further, but I'm not sure.
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