How many fish can fit in a 20 gallon tank?
Mollies should really be in a 30 gallon. Though baloon mollies would work, You would want small, 2 inch or less tetras, like neons, or glolight, lemon, bloodfin, or ember. If you want fancy tailed guppies, I would skipp the mollies, they will bite their fins. SOO, 3 same sex ballon mollies and 9 of the small tetra, OR 8-12 same sex gupies Or 15 ember tetras Or 3 same sex guppies and 7 of the small tetra
20 gallons of fish