As Corty said, it's more like a "rule of thumb". I dunno what that means totally, but it's not characterized as a "rule". It's still a good rule of thumb. You gotta consider the audult size of the fish - since we do plan on keeping them to maturity. Also gotta consider the filtration, amount of LR
, and maybe some other things.
I definitely wouldn't say it's an awful rule or it should be thrown out.
Beacious - Try the calculator above @ this site for the "rule of thumb". I think its based on 1" of adult fish per 5 gallons.