A lot of the listed fish ave their own requirements. shoaling fish generally seem to do better in longer tanks. Zebra danios, i know, need a tank 30 inches long- or even longer, they're wild- and that's a 20L or bigger.
of course, like with any fish, you should research their needs before deciding whether they will fit with your bettas and in your tank. Water requirements are just as important as tank size so be sure you know the hardness and pH of your water before choosing too :)
Very good suggestions, Elliriyanna!
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