I used some black plastic netting for trees that I found at Home Depot. I held down with screws put in the edge of the tub. It worked okay, but raccoons still caused problems on occasion, as they fiddled with the water pump in the tub. Twice, they redirected the output so the tub was almost emptied. Another time, they pulled the pump out, around the netting! In short, if raccoons are in your neighborhood, you really need to secure the pump!