Most people preffer to remove eggs before they turn into tadpoles (with the exception of "egg-feeders" like D. pumilio) and then rear the eggs and tadpoles outside of the terrarium. I raise my tadpoles together with other tadpoles from the same clutch in shoe box size plastic containers. Other people raise the tadpoles in individual cups or containers.
Mixing species from different genera has potential to work but it's safest to start off housing species individually. There are a number of problems that can occur when different species are housed together that normally wouldn't and someone with little or no experience keeping dart frogs might not catch them.
It's an absolute pain to service pumps that are under false-bottoms. Everytime I've tried it I just end up getting sick of fixing the pump or replacing it and end up giving up after a year or two. Right now I have two terrariums with false-bottoms that have broken or clogged power heads sitting underneath them because I'm hesitant to tear apart part of the tank to access them. To make access to the pump easier a section of egg crate can be cut out above the pump and placed on its own individual spacers to create an access door but you still have to dig everything up around it in order to get to the door.
Start with a species that is bold, hardy and large. There are a number of species that fit that description but D. azureus, D. tinctorius and P. terribilis are three that come to mind. All species are a pleasure to keep, even shy dull species/color varients are a pleasure to care for. If I was going to start all over again I'd go with D. azureus because their colors are stunning and they are extremely bold but everyone I wouldn't say it's my favorite or "the best" frog. Good luck with your dart frog ventures,
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Devin Edmonds
devin@amphibiancare.com
www.amphibiancare.com