Good Day All!

I am getting prepared to set up an enclosure for Amazon Milk Frogs.
Hoping to get 2 or 3.

Right now I have an 18x18x36 headed to me in the mail (Josh's Frogs stated this is large enough for 2-4).
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While they're still young, I'll be using eco earth as substrate. When they get bigger, I'll convert to fully aquatic.
My home stays between 70-80 year-round, so do I need to invest in a heater? Or will they be fine in this range? And of course, I'll be getting a thermometer/hygrometer to help me maintain these.

As for filling the tank with things for them to climb on, I'll be getting a mangrove root style "decoration", so it will last once converted to full water. Is there any kind of wood that will last permanently in an aquatic setup? Or should I just stick with this plastic? I saw some beautiful grapewood online but I don't want to shell out that much money if it wont last.
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Other than that, an assortment of vines and foliage.
I'll also be getting fake water lettuce and duckweed for when I switch to water.

Do these guys NEED UV lighting, or will D3 with their calcium supplements do?? I'm reading a lot of mixed info on this.
There will be light regardless, but what info I receive on here will dictate whether it's UV lighting or just something simple for day/night cycling.