Would a school of 9 of them be large enough? That's about as many as I can afford with the shipping included, but if they wouldn't do go I'd scrap the plan of getting them.
Right now I feed my crew New Life Spectrum betta formula, Fluval Bug Bites, and Frozen bloodworms and brine shrimp. Would the Danio need anything else? The site says they are omnivores, and the diet I feed tends to be high protein for the betta.
My water is somewhere around 7.4 and 7.6 PH, will that be O.K. for them? I know that they prefer more acidic water but monkeying around with the PH scares the heck out of me, I'd probably never keep it stable.
My tank is established, and heavily planted along with having some hard scape spread throughout, so plenty of hiding places. Cinnabar the beta is pretty laid back and doesn't take much interest in the cory cats.
I think you woulds have a great mix for a 20 long. If your problem is keeping the PH at a higher PH balance Check your substrate to include Aragonite and ad either rock chips to larger pieces of rock that will raise the PH naturally. In order to regulate this mix I would take readings before adding any rock that would raise the PH and then again 24 hours after adding a few rocks at a time until the PH is where you want it to be. This would also insure that any fish in the tank could adjust to the rise.