What qualifies a nano tank?

[mark]

had thought a nano was less than a 20g, with a 20g being a small tank or if really wanting to push it, a large (largest) nano.

[mark]

went over to Nano-reef.com to see how they define themselves:

Nano Reef

A small reef aquarium, generally 20 gallons or less. Also known as nanoreef or nano-reef.

[JDigital]

^^ And yet over on NR there are sooo many people starting up 40Br tanks..

Must be a "Nano" thing, cuz I don't see many other non-nano reef forums with many 40Br builds...