I have been doing research on this combination myself. I found mixed information. One side said that they are fine together, another side said that CPD are too hyper stressing out, and out competing dario dario. I talked to my LFS guy that has kept nano tanks for a long time. He has kept them together without any issues at all. Having said all of that. These fish should be kept in a minimum tank size of 10 gallons. I haven't found any fish that should be kept in a tank smaller than 5 gallons as of yet. I hope this helps. Good luck.