two very lonely fish

So I've got a 5 gallon tank that I originally had a betta and two albino corys in. Betta died (had him for 5 years) and unfortunately one of my corys got stuck between a rock and the glass and died. I rearranged my tank to prevent that from happening again.

Then my husband came home from work (he's a contract painter for an apartment complex) with this little flame tetra. Somebody moved out and left their aquarium behind and all but one tetra died.

So now I've got a 5 gallon tank with one lonely tetra and one lonely cory.
My question is: how many fish would be comfortable in a 5 gallon tank? Should I just buy a 20 gallon and get more tetras and corys?

Thanks everyone.
P.S. I'm new here!

 

I would get a 20 and get more corys and tetras

 

Agreed, 20 gallon long would be ideal to up your corys and tetras to at least 6 each of the same species as they are both schooling/shoaling fish.

 

I would buy a 20 long so the fish have more swim space, and use the 5 gallon as a QT.

 

Thanks everyone! I'll post photos of the new tank once I get it setup (if I can figure out how to upload them)