That’s a nice footprint size but 18” height is tight. You have a drainage layer and substate which is using up a chunk of the height. You are trying to build a “naturalistic” enclosure and darts spend a lot of time climbing up trees. You have not used the full height available.
Maybe add some branches and try to fill the unused space in the upper portion.

 

Adding more magnolia leaves would a good thing. You have a good base of leaf litter, but larger leaves are easier for frogs (especially tincs) to hide under.

 

I'll agree with what @50’s Mark said and add that your substrate mix is going to retain a lot of water. Reptisoil isn't great for darts since it retains so much water, ditto eco earth. There won't be much drainage happening until the substrate is completely saturated, which isn't ideal for dart frogs.

 

You can add small coco husk planters into the side walls and add some back coverage so the space isn’t wasted. You could buy more branches to come off the walls as well. I’ve also done a wood branch “bridge” recently across a corner that my frogs use all the time. With 18” height (I have one that is 18” high as well) you need to make as much of the empty vertical space usable as possible (if that makes sense). They won’t use the vertical space much if it’s essentially a cliffhanging experience. 😉

 

Thanks for the advice everyone. Looks like I did pretty much everything wrong. I was thinking that I needed to leave some space up top for the plants to grow in. I wish I had found this site earlier. I was mainly getting my information from YouTube videos. I'll break everything down and ditch this substrate mix and redo the hardscape to include more climbing options. After reading several threads I may just go with aquarium filter foam for the drainage layer, a thinner layer of substrate, and deeper leaf litter with more magnolia leaves. I have an 18x18x24 that I was going to start building soon so this information will definitely help moving forward with that build also.

 

 

Here's what I plan to do for the rework of this terrarium. I just thought I would get your opinions before I break it down and start cutting out background. The pieces of wood are just crudely wired up for the purpose of the pictures. They kept falling out of place so they won't be in these exact positions when they are foamed in. The red lines are more where I plan to put them. I'm going to put a piece of cork bark on each of the side walls to add some platforms towards the top. The 2 pieces on the back wall are 4-4 1/2 inches wide each to add climbing spots in that upper area. I will also silicone 2 pieces to the vertical wood in the middle to try and achieve somewhat of a root system look. That will help fill in some of the empty space towards the front and add more climbing opportunities or some cover whichever they prefer. Do the changes look like it will be good or do I need to try and add more? For the substrate and drainage layer, I have decided to use 1.5 inch 35 ppi aquarium filter foam with 1 inch of gravel and a thick layer of leaf litter on top. I've never planted in gravel before. I'm not particularly worried about most of the plants, but I am a little concerned about the jewel orchid and the Selaginella. Should I use a planter and soil with those?
The first picture will be the original so nobody will have to scroll up to see it.

 

So here are the results of the rework. I decided to go with a false bottom. New substrate is primarily pea gravel I did mix in some charcoal, fir bark, and calcined clay for some moisture retention for the terrestrial plants. I'll add leaf litter after the plants get established. I still need to order a few bromeliads to add into the empty spaces. I think they will be happier with this design than the original one. Much more climbing opportunities for them. I appreciate the advice everyone gave and please let me know if there is anything else.

 

Mixing the bark, clay and charoal in the gravel seems to be defeating the purpose of why using the gravel in the first place..

The next thing is more personal preference, but I feel like everytime I see the 'vibrant purple light tanks' like it entirely destroys the look of any of those tanks.. a 'daglight white' (and not overly bright) is imo so much more pleasing the the eye and overall look of the tank.. might be something to consider unless you dig the 'purple/artificial look'.


Again, this is purely personal preference.


Greets,
Tijl