No fish. No dwarf frog.
The smallest aquarium suitable for any fish is 5-gallons, and with that you are limited to a single Betta.
ADFs need a minimum of 10 cycled, very well established gallons in which perfect water parameters are maintained.
If your 3-gallon is heated and filtered, you could probably get away with a planted set-up stocked with a single snail, and 1-2 small shrimp.
Edit: (In regards to the uneducated advice below.)
If only it were so simple...
Not only is the 1" of fish per gallon of water "rule" a bunch of hog wash, there is also the minimum tank size to consider for any fish, along with their activity levels, minimum groupings, and water quality issues.
I'd give the stocking examples provided somewhere between an hour and one week before all were dead. Geash.
The smallest aquarium suitable for any fish is 5-gallons, and with that you are limited to a single Betta.
ADFs need a minimum of 10 cycled, very well established gallons in which perfect water parameters are maintained.
If your 3-gallon is heated and filtered, you could probably get away with a planted set-up stocked with a single snail, and 1-2 small shrimp.
Edit: (In regards to the uneducated advice below.)
If only it were so simple...
Not only is the 1" of fish per gallon of water "rule" a bunch of hog wash, there is also the minimum tank size to consider for any fish, along with their activity levels, minimum groupings, and water quality issues.
I'd give the stocking examples provided somewhere between an hour and one week before all were dead. Geash.