Here is the Vet Tech GF...
Heartgard Plus to protect against heartworm, roundworm, and hookworms- In AZ the number of heartworm postitive dogs is on the rise and since it is a painful thing to treat it is highly recommended to use a preventitive. Most good veterinarians require anual heartworm tests to make sure all your dogs are negative before starting, because if they are posititive and you give it they could go into anaphylactic shock, which could be deadly especially to small dogs. Interceptor is also a good product.
For ticks I'm not sure what kind are in your area you would have to talk to your vet when you go in for the heartgard and HWT. Any prescription preventatives are usually safe, some breeds are more sensitive than others, but as long as your dogs are healthy before application Advantix and Frontline are usually good (don't buy from Walmart OTC because who knows what kind of shipping/storage systems they use, these are prescription drugs and need to be kept at a certain temp)
I know vets are expensive but it really is in the best interest of your pets. Hope this helps!:thumleft: