Very nice pics, you make me wish i could visit this aquarium.
In the wild, dart frogs level of toxicity ranges from the as-long-as-you-don't-lick-me-you're-fine level to touch-me-with-scratches-on-your-hands-and-you-die. Some species might makes your hands tingle for a while, and of course you do not want to touch any sinus membranes or mouth after handling. I've caught a number of different species though and noticed no effects at all.
Once in captivity, toxicity rapidly dwindles, so there seems to be a wild diet connection. Very interesting.
There's a lot of beautiful frogs out there, but my favourite thing about Dendrobatids is their personality--an unfroglike boldness, hopping about in the open throughout the day, displaying and wrestling and such.