I have a ten gallon for my wife's froggys. We have 3 african dwarf frogs. What else could we put in there that wouldn't get too big? I would like to find some kind of FW crab that wouldn't disturb the ADFs.
You'll see below what I have in my 10 gal with my ADF. I do think you'll have a tough time finding a crab that won't take a leg or two off your froggies when they get a chance though...
Don't have first hand experience with shrimp. Mine is with a male betta, among others, and they get along fine except when the betta tail is mistaken for food...that frog got a hell of a ride around the tank that day! (and did no damage to the betta tail he held onto). Also you will have to take care the frogs actually get the food...
You might do well with dwarf cories or regulars ones (they keep the place clean and go good with a betta). Any other community fish that can live in a 10g tank will probably be fine with the frogs. Just be aware that if the fish can fit in the frogs mouth (fish fry sized fish), it is food, and those frogs are quick!
I also don't think there will be any type of crab that can coexist with the ADF's peacefully, since the crabs will try to eat the frogs. Most people keep a single male betta with the frogs, which is a good idea IMO. I think also a small schooling fish would do well with the frogs. I have some white cloud minnows, and they are very active and interesting. They are also very peaceful and can coexist with the frogs. The frogs will stay at the bottom for the most part and the minnows swim in the middle and upper levels most of the time. Even if they did encounter each other there would be no problem.