The aerator in this faucet is supposed to be removed unscrewing by hand. No tool needed. This isn't really true. Fact of the matter is the aerator has very little to actually grip onto for unscrewing. I also believe the Delta factory is likely screwing in the aerator tighter than necessary. To remove mine I used a tall glass and soaked the end of the faucet in 2 inches of 50/50 vinegar and water for 5 hours. Ensuring the aerator was completely saturated in the solution. I did this in case any build up was making the aerator stick. I'm not sure this is the case because I only run RO with softened water through this faucet. After soaking I dried the aerator to reduce slipping. Then I took a channel lock and wrapped the teeth in electrical tape to protect the faucet's finish. Set the channel lock width to the aerator and unscrew with a firm grip, but don't squeeze too tight and bend the aerator into an oval shape. The aerator should turn a little and from their you can unscrew by hand.