Does anyone know what kind of filtration he has on his guppy tank?

Love it! The knowledge of fish is priceless friendly service. I can manage my tank its clear smells cleaner thanks guys.

There appear to be at least a dozen guppy tanks, all hooked up centrally with filtration via air bubbling. Possibly CO2 (his plants are outstanding). Often the gas lines enter the tanks through cut-up bottles stuffed with layers of filter media. There are actually several tours on YouTube if you want to try to inspect yourself, just search for "Ocean Aquarium San Francisco".