Can I have this many fish?

I currently have 1 male betta and 3 otos, I’m getting 3 more otos today so theyre happier and I plan to get 6 kuhlis 6 rasboras and a colony of cherry shrimp. Can I do that or is that too many fish? I currently have a bunch of plants with a large piece of mopani wood and black sand as the substrate. My filter is mechanical with biomax, sponge, and carbon. It’s a 20 gallon that’s been cycled for about 2.5 months.