Please avoid the Hartz brand like the plague. Its known to cause many troubles in cats and dogs, even while used correctly.
My dog doesn't not suffer from fleas - they are not as prevalent where we are, so I don't know any homeopathic remedies for fleas - although the orange peel oil is supposed to be effective and safe (you can buy sprays like that and spray them on the dog directly with no ill effects). For ticks, I've had pretty good success with garlic. I was feeding raw for a while, so I would just grind up a bunch of garlic with the veggie mixture I made him, now I just put a chopped up clove with his breakfast and dinner. It's not perfect, but ticks are attracted to the smell our the carbon we exhale, and this seems to change the attractiveness of Jimmy. When I had my foster and did not feed him raw, he attracted ticks like no one's business. As soon as I started mixing the veggie mixture into his kibble, he became much less attractive (we hike in tick country a least once a week).

