Your cherry shrimp will be safe from your frogs. Marsh frogs are primarily terrestrial, although they do spend a lot of time in water. If placed in an aquarium with just water they will drown. They forage around the edges of water for insects, spiders and other small invertebrates. They will even take these things from the surface of the water but not underneath it.
I use cherry shrimp, along with a bristle-nosed catfish, as the clean-up crew in my aquaria. I have read a lot of “you must do this or that” with regard to keeping these shrimp. However, my experience is that they are extremely hardy and don’t need pampering. My aquaria are planted to help maintain water quality and reduce the frequency required for water changes. The shrimp showed a preference for hanging out in the java moss when I first put them in about 20 years ago. It seems a good food source for the biofilm they eat and provides protection for the tiny shrimp while they develop.
I even tried a little experiment where I placed sonly some java moss in an old style fish bowl along with some tiny shrimp that made it through the fish net I use when I vacuum the tanks. It was placed on a bench where it got some reasonable afternoon light, but no direct sunlight. Initially I added a tiny pinch of fish flakes and then pretty much forgot about it until one day I noticed some movement. By then there were four fully grown shrimp in the bowl.
If at some stage you decide to get rid of your shrimp, do not release them outside or flush them into the sewerage system. They clearly have the ability to establish self-sustaining populations in Australia if they escape into the wild. Aquarium shops would probably take them or they can be used as a natural live food for cichlids or similar fish. They also make great turtle tucker.
Good luck with the frogs.
