I have used granules for years around my pond and never had a fish kill. If the mounds are withing about 10 ft of the bank I pour boiling water on the mound, it doesn't kill them but they get mad and move and hopefully it will be away from the pond where I can get them. I have been battling them for about 10 years they will get inside the greenhouse and into the pots that I have plants in. No fun to pull a weed out of a pot and have 50 on your hand!

Bob in North Alabama