The first tank I ever did was a vertical conversion on a 29 gallon for some tree frogs. I used styrofoam boards that I sprayed GS (Great Stuff) onto and then let it dry. After it dried I cut cliffs and stuff into for the frogs to hide in and on. After that I covered the GS foam with GE 100% Silicon, you want the stuff that is for outdoors and for windows and doors. DON'T get the stuff that has antimold stuff in it (i.e. bathroom and kitchen) I REPEAT DON'T use the stuff with anti mold. As I was putting the silicon on the GS I covered the silicon with a mixture of coconut husk and plantation soil.
There are TONS of ways to do it but for darts you'll want to make a big log or branch your center piece and then GS around that so the frogs have a way to climb up the wall.
Easiest way to do that is silicon the log to the glass or even just use the GS to hold it as long as the bottom of the log touches the ground so it has some support on the bottom.
Thad