I havent bought any frogs yet but will be going to a reptile expo over the weekend and know i want to get some dendrobates but also want to make sure they are healthy and happy. I have already purchase the Exo-Terra PT2607 terrarium; 18x18x24, about 30 gallons. The question is what number of frogs can I comforatably support within this environment? I wanted to have two types of frogs in one tank for aesthetics, specifically azureus and auratus. I know morph mixing or interbreeding is frowned upon but my studies have lead me to understand azureus and auratus will not breed with each other. Also, I understand azureus live best in sexed pairs due to hostile mature females. They tend to ignore auratus because they are not sexual competors thus alleviating potential sources of stress found from inter-species co-habitation. The remaining question, if 2 azureus can live with 2 auratus, is 30 gallons enough for them to live together healthily?
If anything I have said runs contrary to your investigations please let me know. I am less than a novice and eagerly seek the knowledge of those more experienced and am truly appreciative. Here's a link to pic's of the terrarium i am buying. Thanks a bunch.
exo-terra pt2607 - Google Search
Can you share where you have seen some of this info? It seems you have been mislead in some areas:
Azureus is a type of tinctorius, and will breed with auratus. So crossbreeds are certainly possible.
You are correct about azureus doing best in pairs due to female aggression; however, aggression does not only occur over breeding competition. Regardless, as I said before, they can hybridize and so you would still have the sexual competition.
When I first started out, and the pet shop was my only advice because I had never heard of Dendroboard or any other places like this, I kept a female auratus, an azureus, and a juvenile male leucomelas together in a 40 gallon. The auratus female was so aggressive to the azureus (and this was a sexually immature azureus, so no breeding competition) that she killed it in a week due to wrestling. That's when I started to realize that pet shops don't always know what they are talking about, did some research, and of course got them separated.
So, I would suggest that you find one type of frog and stick with it for this tank. Either a pair of azureus (you might even luck out and get a 2.1 trio to work, but not always...), or a group of 4 auratus, or a whole different frog if you want.
Keep up the research, and any more questions don't hesitate to ask. One last thing- I know you may want to try to get different species or morphs together in one tank, it seems almost all new people do, but it is frowned upon in the hobby; properly mixed tank usually require very large vivariums, and a 30 gallon just isn't going to cut it. It's perfect for a group of the same species and morph though

Good luck,
Bryan
*edit: I didn't even notice at first, but as camlov2 pointed out, both auratus and azureus are more terrestrial frogs, so the height would not be utilized nearly as much as floor space. Try getting one with more floor space, or, if you want to keep the tank and already have it, look into a beginner frog that uses height as well.