I've never seen them in a pond. Shot several of them when younger in lake or bayous in Lousiana. They are vegetarians. Not sure exactly what vegetation they eat. They were brought to La. from South America to eat a certain species of water weed. They may have nibbled on it, but concentrated more on other vegetation they found. You might leave them alone for a while and see what happens. They have the brain power of an armadillo and should be easy to kill should you so decide.