Originally Posted by ladayen
The one inch of fish per gallon is just wrong, completly wrong.
It's an overused theme set by petstores mostly. Not saying it's really right or wrong - though in most cases...wrong. Depending on the type of fish, you can vary in numbers.
Like I said before, tiny fish like a school of 5 guppies or up to 2 bettas can fit happily. Just be sure they have plenty of room to move freely, feed, breath, hide, and explore.
Overcrowding, as I'm sure you know, can lead to death from stress or illness. Also, if you put more fish in there, no matter the size, there's more waste and ammonia, which means more cleaning or your fish will certainly become ill.