my first frog paludarium or terrarium.

so i have 1 tree frog and 2 tadpoles that will be going over to a planted 20 gallon long terrarium or vivarium(i gotta figure out what kind of frogs they're first). i need help with a couple of things.
1.do tree frogs need a paludarium or does it depend on the species?
2.whats the best substrate for plants thats safe for frogs?
3.what are some good plants for the water and on land?
4.i have an internal filter that was previously used in a crab tank which means there is probably salt in it. so whats the best way to clean it?
5.what kind of light should i use? i was thinking of just the light from my window but only about half of the tank is in front of the window.
ill have further questions but thats it for now.

well not all frogs need a large body of water. some just need humidity high.

so a 20 gallon long with lots of plants wouldnt be suffcient? im going to eventually upgrade them to a 40 gallon breeder when i get the monay.

so a 20 gallon long wouldnt work for a little while? what about a 20 gallon long standing up? it'd be 30 inches tall but then what about water? would a water dish suffice? i amagin humdity would be hard to keep up with withought a large water source since i have a screen top.