dart frogs are easier to keep and there is a great place to learn about them. Dendroboard - Your source for dart frog information. they should be able to answer all your questions
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So what type of setup would you like ? ex: will it be a tropical setup with a water section or just wet land ? there are many things you need to keep in mind before starting with a terrarium and i can help you out with some of your questions
There are lots of safe plants you can start with check out Black Jungle Terrarium Supply . usually people use a mix of substrates. Also will you have a false bottom ? (raised land to allows excess water to collect at bottom) also you will need to setup a drain system to get the water out of the bottom of the tank.
So what type of setup would you like ? ex: will it be a tropical setup with a water section or just wet land ? there are many things you need to keep in mind before starting with a terrarium and i can help you out with some of your questions