I've kept it simple. I only mix one species of Dendrobates with one species of Ranitomeya. I will not mix anything that might interbreed. My upper 'canopy' consists of things like ferns and other plants that cannot support the weight of Dendrobates, but easily supports the weight of Ranitomeya. I also have lots of nooks and crannies for hiding. I feed a combination of Hydei and Melanogaster and in large quantities. Dendrobates go for the bigger flies first, and since the smaller flies climb the walls quickly Ranitomeya doesn't have to come down to feed if they don't want to. I believe the success of my tanks largely rests on the feeding I do. I feed every night, and if I don't have left over flies crawling the tanks in the morning I feed more that night. I ensure there is never competition for food. I've seen newly morphed Ranitomeya froglets climb out of the water right in front of a Dendrobates and they are ignored. Have I had any tads/froglets eaten? I don't know, perhaps I have but I have never witnessed it, and I have never had an altercation between adults of the two species. What I have on their own is Phyllobates terribilis. Those guys eat anything it seems, so I have not even attempted to see if they'd leave another frog species alone or not. I think trying to mix terribilis with anything smaller than them is borrowing trouble IMHO.