in search of small fish for my aquarium

I have a 4-liter tank with air pump (your biOrb tank), Its been a year with a male and female betta as tank mates. I just wanted an opinion if I may add one more fish to the tank. If so, what can I go for. The male and the female is doing well and along its been over a year.

The Betta is the fact get along in such a small space is large. No more partners aquarium for them … in a place so narrow, and as they are doing very well together, could upset the balance that currently have. With the Betta male will usually show the assault on another man specific Betta and other fish … and female Betta (especially after breeding). If you get a bigger tank, and place the Betta with other fish, be sure to stay away gourami, guppies, and colorful fish with fins. Be careful with pincers so well … Beards like Tiger, Black Skirt Tetra and the angels … are much faster than the Betta .. and attack their fins. On the one inch per gallon rule … and fish / gallon rule … These are totally false. examples of why … one inch per gallon … if you have a fish that is 10 inches long in a 10 gallon tank … that the rule is feasible, which not take place since turning 10 gallon tank is only 12 inches in width and height. It would also be laying horizonal with the tank half the size of the tank and swimming will not take place. To fish a / gallon rule … I have 1 fish that is 10 inches long in a 1 gallon tank … LOL! Impossible be compatible with long life. Either way, there is a general minimum deposit requirement, with different species and sometimes can skirt this only if the filtration is more than necessary and the tank is too small for the size of fish … and have a margin of swimming. Best of Luck!

biorb