Hey Rocky! Three cheers for FROGS!!! I love my little ADF buddies. . . all positive experiences from me!
Looking over your list, as far as frog
compatibility is concerned, I think you should be fine. . .
ADF and Kuhli loaches were a match made in heaven in my tank, and the only problem I had with livebearers was their greediness at feeding time (you'll usually have to hand or target-feed ADF kept in a community tank, so be ready for that!)
I've never kept my frogs with Betta, but there are a lot of people who do - this is usually in a smaller tank, with a male, and seems to depend on the fish's personality, from the accounts that I've read, I imagine it should be an okay pairing, but you'll want to pay close attention to things. Ottos are *usually* good tank-mates, from what I've read, I haven't gotten to keep Ottos yet, personally.
In my experience, ADF really do best in a species-only setup, especially while their keeper is new to them, and still learning how they are - frogs are completely different animals than fish, and have different needs. When they're kept with fish, you really never can be sure what will happen until you try it - so you'll want to be sure that you have a tank ready to keep your frog(s) in species-only if that becomes necessary - in my personal experience with these animals, that's really the easiest and best way to keep them (though mine are currently in community, too)
So as far as the FROGS are concerned, you should be okay, but I recommend that you go back and do some additional research into the needs of each of these animals before bringing them home or moving them into this tank.
Loaches won't be happy unless they're kept in a group, you should probably get 6 of them so that they'll feel safe enough to be out and about and show you how awesome they are.
Otos are shoaling fish too, so from what I've read, you'll want to bring home a larger group than two. I haven't been brave enough to buy these little beauties yet, because it can be difficult to acclimate them, and they need a very specific algae-based diet to thrive - very different from the protein-based diet that the frogs need. This is just what I've read, and I haven't done *much* research yet, so please double check me. . .
Both Otos and Loaches need very stable tanks, fantastic water quality, softer water, and do best in a well-planted setup (not sure what your tank(s) are like, so thought I'd throw that out there.
I don't know much about Beta fish, or sororities - but I'd definitely want to look into that further (if you haven't already)
Livebearers should be safe enough, but some of the other fish on your list need soft water, while guppies like their water a bit on the harder side, so check water parameter (and temperature!) preference for all of these before adding them into one tank.
I hope that helps a bit! I'm sure someone will be around with more experience to add it at some point. Congrats on the soon-to-be set up 20g! Can't wait to see where it ends up! Good luck, and happy researching ^_^
