Originally Posted by Lupin
The inch per gallon is bunk. This is only a guide to avoid overstocking but even the rule itself cannot clearly justify which species will work with a particular tank size bearing in mind it will not make sense to keep a 10-inch oscar in a 10 gallons which most beginners often interpret with. Compatibility, space and other factors are to be considered. If I were you, stick with the betta or get a larger tank if you really want to add more fish.
I do realize that ther are other factors to keeping fish in a tank. However, I was trying to make the point that a 3 gallon is too small for more than 1 fish.
Most of my life I have had tanks that were 25 gallon or 50 gallons. In fact the 50 gallon tank save my family's life and home when I was a child. There was a fire that started for the eletrical outlet that in the room our big tank was kept, close to the tank. The heat and stress caused the glass to shatter dousing the fire and waking my parents up. They were able to get us up and out of the house and have the neighbor call the fire department. When the fire department came and saw the remains of the fish they wedre shocked at the size they reached. I believe one asked my mother if we ever fished in the tank.