Agree, a 10 gallon can only hold 12 males endlers! If you want a colony then get a bigger tank and just get 1 male and 2 females. After 2-3 months you will have a good colony
In a 10 gallon you should only have a betta! If you want another fish I suggest splitting the tank and get another betta or endlers. Don't try to create a community tank!
We don't recommended it but sure you can try but just keep an eye on them! They are small so the betta can try to eat them!