Join Date: Jul 2015
Location: Orange County, California
In my personal opinion, <10 is nano, 10-20 is micro and then from 20-39 is this weird limbo space, 40 -70 is a "regular" sized aquarium. From there to about 200 are large aquariums, 200 to 600 are big aquariums, and more than that is a super tank. This is coming from someone who has a 5, 10, 17 and is setting up a 112 as he types this.
It's all relative like tropicalmackdaddy said. If you're wondering for the purpose of flora/fauna stocking options, I'd say looking for "nano" options would be a safe bet.