Thank you MinorHero,
I was hoping to create a gentle slope at water level to support the frog if it goes for a swim. I heard Dart frogs, as you said, have a hard time in the water, but also, that they can swim ok.
I was not planning on a canister filter, as this is my first paludarium and I'm planning on putting it together inexpensively. I'll probably get a submersible pump/filter to create a waterfall to support oxygen in the water and humidity, something like this (https://www.amazon.com/dp/B086ZQY17T...ing=UTF8&psc=1
). Do you think a heating pad on the side of the tank would create a risk of the frog burning itself? Else, I'll probably use a heating element, or an incandescent bulb.
I'm assuming that you are planning for a dart frog?
If so, then 1) you do not need a heater. Dart Frogs are ideal at temperatures ranging from 65-75 and can go for periods both a bit warmer and colder. So long as you are not staying in the 90s+ or 50- then they will be fine. In fact you are better going cooler then hotter as they can start to die in 80+ degrees sustained temperatures depending on humidity. Even LED lights will add 2-4 degrees just by themselves so if your house is at 70 degrees then you not only don't need a heater, you don't want one.
2) Unless your tank is providing at least 36 inches of horizontal space I would skip the water feature. There are some misconceptions going around about their ability to deal with water. Its not that they can't swim, its rather that a dominant frog fighting another frog can drown the less dominant frog in water and this is the easiest way to lose a frog. People might not see this though and instead just find a dead frog drowned in water and assume they couldn't swim. Even if you don't have this issue water features are harder to maintain in a dart frog tank then say an aquarium because a) frogs poop in the water which is a lot of nutrients going in that won't get filtered out (poop being too big to go through a filter), b) feeder insects and clean up crew can and will die in water at a rate at least equal to the frogs eating them, c) vitamin dust will get in the water fouling it, d) the water tends to stink and become discolored because of the reasons just mentioned, e) water features tend to DRAMATICALLY increase humidity and dampness of substrate in tanks. This is a huge problem because the frogs need to be kept at 60-80% humidity with options to dry out completely during the day (ie not stand on something wet) or they will develop bacterial and/or fungal infections of their skin. These can be dramatically horrible ways for the frogs to die, and finally f) while the dart frogs won't ignore the water feature, they also do not need the water feature and thus its a space that is wasted from keeping the frogs.
If you have at least 36" of tank space you have enough room to include a water feature and still have room for the frogs to do their thing. Even then I wouldn't include an open water feature like a pool or stream. Instead I would do a dripping branch/rock/wall section leading straight to a gravel bed where the water goes down into the substrate and does not pool on the surface. Speaking of substrate, in any tank that has a water feature your substrate needs to be aquarium friendly (since this is basically what you are making in the tank). So no ABG mix. Instead go with aquarium aquasoil and/or calcined clay (like turface or safe-t-sorb). These substrates don't fall apart and rot when exposed to water.
If you decide to go with a frog that is not entirely terrestrial (like a reed frog) you won't have the same issues with the frog dying from excess damp or humidity. You will still need to find ways to deal with your water feature not being super yucky but at least then you go into it knowing you need the water feature.