Fruit Flies Dusting - I have a link to my youtube channel in my signature. There is a Fruit Fly culturing how to video and in it I also included how I dust my flies.

Foam sounds like it could be really cool. Just keep an eye out for it pulling free of the glass. Easier to address it now than after the frogs are living in the tank.

Some wines would do good in there for the Luecs since they love to climb. Some Repens, Lipstick VIne, Wondering Jew... to name a few.

Begonias, Ferns ... Bill is our resident plant nut. He knows all the cool ones and knows their names. I will see if I can't scare him up for you.

18x18x24 is borderline big enough for 3. 2 - 3 in an 18x18x24 is doable, but a 24x18x24 the would probably enjoy more.