Here is the link to Mark Staniszewski's Mantella FAQ....
http://www.amphibian.co.uk/mantella.html
I highly recommend purchasing his harcover book... it is expensive, but is well worth the money for the wealth of information it yields.
As for the poison... that is basically it. The frogs in the wild eat insects containing alkaloids. The frogs then process and refine these alkaloids making them far more potent. So basically, I have been told to think of these animals as alkaloid refineries.... they do not produce the toxin themselves, they only modify a chemical in their diet. This is of course, just a general non-specific explaination...... Wild frogs will lose their poison as time progresses, and CB frogs are, for all intents and purposes non-toxic as far as I know.
Good luck with the mantellas. The setup sounds like it will be nice. Be sure to post some pics when you are done.
Double J