Fleas and reptile mites are different, one feed on warm blooded animals the other on cold blooded.
For cold blooded animals you want to use something that takes care of eggs and adults, people usually do their own mix (I do not recommend it if you do not know what you are doing)
or use Provent A Mite or a cheaper Alternative and it is of course important to treat all animals not just the one that have the issue.