Should i buy new fish for my tank?

[Paigeyy]

I have a 20 gallon tank filled with about 16.6 gallons. It's separated between my male and female bettas. The tank's so large and it feels like a waste of space, so i wanted to get them a couple tank mates. I'm currently working at a pet shop where they have mollys and a dwarf gourami for sale and i wanted to buy 2 mollys to put with my girl, Caboose, and the gourami to put with my boy, Tex. Is this too much for my tank? or would it be okay?

[Silverfang]

I can't comment on the stocking plans, aside from the fact gouramis and bettas should not be housed together

[Gizmothefreaky]

Bettas and Gouramis are from the same family and will fight just like two male bettas, and Mollies prefer brackish water, which bettas cant handle.

[Bombalurina]

Rather than mollies, have a look at platies. They do fine is freshwater and are less aggressive. :) They also stay smaller and have smaller bioloads.

Definitely stay well away from dwarf gouramis.