Tank Mate advice

20 gallon freshwater, GH and KH numbers are high (hard well water mixed with store bought spring), ph around 7.5-7.7, temp 78-80 F
5 marimo moss balls, tiny amount of growing java moss, driftwood, cholla wood, gravel substrate

Currently housing 6 african dwarf frogs, 6 ghost shrimp, 7-9 red cherry shrimp (hard to count). I want to add some kind of mid level fish but I'm not sure what's best for my current members. I've read some conflicting info. I want something that doesn't require a large school (6+), preferably 2. My shrimp have tons of hiding which is why I don't know exactly how many cherries I have. The ghosts are always out. My frogs do try to nip at the cherries, but the shrimp are too aware and too quick. The ghosts aren't really bothered unless in frogs way to feeding dish. Also I thought about 2 cory cats, but I read ottos are good tankmates for what I have. Can ottos be happy with just 2? I'd like 2 fish on bottom and 2 mid-upper. That's all I want for my 20g. However I don't want to stress anyone out. My frogs are priority #1, the shrimp are basically frogs personal housekeepers though I love watching them. Suggestions please!!! Experience with your own tankmates???

I may do that, 2 ottos, but a few months down the road. I want to add a couple swimmers first. I read about endlers, that they are good companions for adfs and cherries. However it suggested 6+. Anyone have experience with having only 2-3 of them? My main concerns are not stressing my frogs and at least a few cherry babies surviving. With the cholla wood, I believe they will. My frogs can't squeeze themselves in there, though not for lack of trying!

If its mid tank or upper, it would be very hard for them to get a hold of them. They aren't the best swimmers. My cherries are definitely small enough to get eaten, but they are too aware of the frogs and too fast. Most of the time my frogs don't even bother trying anymore. I want something I can have 2 of on bottom, and 2-3 on top. If enough cherry babies survive and I develop a good amount, i'll probably skip the bottom. So can anyone tell me anything on endlers? Being li e bearing they would give my frogs a snack. Could I do 2 female bettas?

I'll look into those suggestions. Thank you. I don't want my shrimp eaten, but i'll be more planted for them soon. I'm not concerned with my frogs eating anyone. I seriously have the laziest frogs ever. Its too much effort to go after a shrimp that's eating their worms right next to them!