How often should my indoor Shih Tzu get dewormed in Florida?

He definitely seems low-risk if he's usually inside. However, Florida's climate is very favorable to parasites and the infective stages can live in the environment for a few months. Depending on where he eliminates and his contact with other dogs, he may be more at risk.

In the past (and sometimes still today) vets would recommend a regular deworming schedule. This is no longer advised, or appropriate, because we don't know for sure if the schedule is appropriate, which can lead to resistance to the deworming medication. The current recommendation is to have your veterinarian test the stool for the presence of worm periodically and give treatment as needed. You can have this done six months from now and then your vet will advise from there.

For more information, I recommend you read the article at the link below.

https://vcahospitals.com/know-your-pet/internal-parasites-in-dogs

I hope that helps and all is well with Harley.