Originally Posted by ChelseaK
The general fish/water ratio is 1gal/in. of fish. Most males are about 2.5 inches there for the recommended minimum space for them is 2.5 gallons. Knowing the gal/in rule makes stocking a lot easier :)
This doesn't apply to all fish though! Just a warning lol My 6" pleco would not appreciate a 6gal aquarium. Also fish like Cichlids need massive tanks due to them needing groups and room for territories. A group of 4" chiclids need 75gal+.
For smaller fish, this rule is 'ok' but keep in mind some fish require groups. My Danios for instance, need 6+ per tank, and something over 20gal. They are about 2" each maybe less. Research is key.
There are smaller plecos that only reach to be 4" though, Bristle Nose Plecos being one.