Endlers In With Bettas

[MegaZerino]

I have a 64 litre tank with a red dwarf gourami and a 5 female betta sorority. At the moment they seem fine, but the tank doesnt seem quite finished or full enough. I was thinking of getting some tetras but i understand that they dont tend to get on with Bettas. So i was wondering about Endlers. I think they can sometimes get on with a single male betta but i wasnt sure about my 5 females. So i was wondering if i could put Endlers into the tank, and if so how many. But if not then what could i add??

Thanks