I have been waiting for my babies to get big enough for Flea prevention. The Advantage Multi I have say they have to be 3 pounds so we are almost there, Arizona was 2.6 and Ace was 2.06 at the vet last week. They told me to wait about a week before i apply it and its been that but i dont think they are 3lbs yet, especially Ace. I know they have a few fleas on them and I dont want it to get worse. I think they are even too small for regular flea shampoo. Petsmart doesnt start till 6 months. I feel horrible when i see them scratching every once in a while. I figured that they would get some fleas since i couldnt treat them but like i said i dont want it to get out of control. Any ideas anyone? Thanks!