The problem is going to be producing enough isopods to be a complete staple for your darts. They are generally slow to mature and reproduce. Flightless/Wingless fruit flies are going to be a much better staple, and you can mix up the diet with bean beetles, isopods, springtails, wax/silk worms and in some species, roach nymphs.

Actually, you could feed adult Phylobates roach nymphs exclusively as they are a larger frog that can and will take a larger prey item. The only problem with roaches is the same/different than crickets. Roaches may escape while feeding and bury into the soil where they will grow quite large. Crickets will do the same but have a tendency to chew on frogs when they get hungry.

The fruit flies can live through a life cycle in about two weeks and produce thousands of flies in that time period from only 100 original adults. And there are many different types of flies, but two species.

I could guestimate that your frog will eat around 100 to 200 flies a day depending on the size of the species of frog and fly!