With any live plant type vivarium, you need at least a gravel drainage layer of about 3 inches, separated from the substrate with something like weed cloth to keep it from clogging up with soil, from which you can occasionally siphon out the excess wate from misting. This is easily done without drilling, with just a length of air line tubing. A false bottom is very useful if you have a water feature. I'm not familiar with the Exo Terra falls, so can't add anything there. But don't give up. As said above, you just need to tweek it a bit.
I know I seem to repeat this often, but a really easy and practical drainage area/false bottom can be made with Gro-Tek hydroponic slabs. They are a cocoanut fiber/latex coarse sponge like material that comes in 6" wide X 3" X 24" or so, that can be cut and fitted together in the bottom of your tank. If you want a deeper "false bottom" it splits easily along the length so you can add another inch or so. You can put aquarium gravel between it and the edges and the glass so that it isn't visible from outside the tank. Then you can cut out ponds or water ways, fill them with smooth rock, fit your water pump into it to pump the water down drip walls or over falls you build yourself. Any water that gets splashed around will drain off nicely so the entire substrate doesn't get soggy. It's actually really easy to do and doesn't require any tools except a pair of scissors and some silicone to hold the slabs together, if you even need to do this. As with any other drainage layer, a layer of screening such as weed cloth keeps the dirt from from the substrate from clogging it up. Once in awhile, and perhaps several times right at first, you will want to drain and replace the water, because it will tend to be pretty discolored from the various tannins and such. This too, can be done by siphoning it from a corner of the tank with air line tubing.
I've also posted these same pictures a few times of a corner bow tank with P. vittatus in which I've used the Gro-Tek drainage/false bottom. In this tank, the pump is in the very back, and the water is directed alone the left side from the top over a fern bark drip wall.


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Patty
Pahsimeroi, Idaho
4 D. auratus blue
5 D. galactonotus pumpkin orange splash back
7 D. imitator
6 D. leucomelas
4 D. pumilio Bastimentos
4 D. fantasticus
6 P. terribilis mint and organe
4 D. reticulatus
4 D. castaneoticus
2 D. azureus
4 P vittatus
2 P. lugubris