Dwarf frogs shouldnt be kept with fish. First they are very shy creatures and belong in groups to feel safe. They also have poor eyesight and rely on smell to locate food in which case fish will out compete them for food as they are also slow food finders. When with fish they become reclusive and timid and more shy and usually hide all day. In s tank with just frogs they will float at the top swim around breed and even make croaking chirps to eachother that can be heard. Also they need sand as food gets lost and trapped between gravel which they cant find and the bacteria between the gravel can give them bacterial infections as they spend alot of time on the substrate. Also a 50 is too tall for them as they need to go to surface to get air. Id permanently keep them in the 10 gallon by themselves and add a few more. I had 6 in a ten gallon and they even had babies. Theyre a lot of fun when in a tank without fish, with fish all they do is hide and starve