Some good enzyme-based drain cleaners are ZEP Drain Care and Clean Earth Brands Earthworm Family Safe Drain Cleaner. ZEP Drain Care received 4.2 out of five stars based on 12 reviews on the Home Depot website, as of September 2015. It rated highly in ease of use, quality and value.
Earthworm Family Safe Drain Cleaner received 3.5 out of five stars based on 11 reviews on the Vitacost website. Users cited its effectiveness and non-toxicity, but some users found it slow-acting.
Enzyme drain cleaners work by having enzymes eat through organic build up. They make for a good monthly maintenance protocol to prevent drain clogs. However, they do not make good solutions for already clogged drains, as enzymes require some time to work.