If your dog swims, clean the ears with this solution after swimming.
Juice from 1/2 lemon
1 cup lukewarm water
Add lemon juice to water. Using an eyedropper, introduce it into the ear. Gently massage the ear canal (this feels like a small plastic tube in the area underneath the ear) from the outside. Allow your dog to shake its head, then GENTLY blot up extra moisture with cotton balls. Do NOT use cotton swabs because they could push wax against the eardrum or damage it.