I prefer to have frogs in species only setups. They tend to be tough to feed, and having competitive fish mixed in tends to mean you spend a lot of time making sure the frogs are well fed. My frogs prefer frozen foods or live foods (like live worms) to freeze dried or flake foods, so you might want to give those a try. Soaking dried foods in selecon, or a similar product that enhances the odor of the food, may work to help them locate the food items. Frogs hunt by smell, so a food lacking odor, even if placed right in front of them, will be overlooked.