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Hi all,

I am pretty new to vivarium/paludarium construction and decided on an ambitious project. I recently built an 18x18x36 Exoterra paludarium. I did expanding foam background with driftwood and cork bark and built up a rock/expanding foam island area for planting.
I have been having a lot of issues with this set up so far. One of my main issues is that the substrate on the island is constantly wet. I am using ABG and weed barrier to allow the substrate to drain (I've checked many times that the water will drain through the fabric). The water does go completely underneath the land, but I made sure that the water never touches the substrate. It is several inches below. Despite that, my substrate is always saturated. Not just damp, but wet. I've already had one plant experience root rot. It's also starting to smell and I'm wondering if that is part of the reason.
I've looked at many construction videos and forums for this and it seems to be standard for the water to run under the land, yet others do not seem to have this problem. Does anyone have suggestions on avoiding this problem? Do people usually put LECA or something under the substrate still even though the water below is essentially a drainage area?

Any help is appreciated and I'm happy to provide any additional information!
 

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Pictures might help people solve your issue, however soaking wet substrate seems to be a common problem with paludariums
 

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soaking wet substrate seems to be a common problem with paludariums
If I had a nickel...I'd be even richer. Ha ha.

Is it possible your foam is wicking? Plenty of times I've demo'd a viv and found sopping wet foam. It takes special care to seal that stuff. IME anyway. "Closed cell" yeah whatever.

Pictures might help ...
Indeed.

Phew.
 

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I've looked at many construction videos and forums for this and it seems to be standard for the water to run under the land, yet others do not seem to have this problem. Does anyone have suggestions on avoiding this problem? Do people usually put LECA or something under the substrate still even though the water below is essentially a drainage area?
I hold the opinion that most viv construction videos are literally worse than nothing. If all you had was written and verbal communication you'd be better off. Visual media are seductive. They also interact strangely with our cognitive biases. So my first suggestion is that you stop watching them. Either cut way back, or go cold turkey.

For avoiding wicking and soil saturation in an "island" or "peninsula" situation, the first question is - what shall be the relative elevations of the water surface and soil bottom? Yes the water below is "a drainage area". But it is also a source of water, which can very easily be transported laterally, and even upward against gravity. The safest (but still not sure) route is to have the soil perched above the water, as you indicate you have done. It is entirely possible to have dry soil below the water level, but it takes good materials and careful, materials-appropriate construction, as well as careful operation (e.g., no incidental splashing at all, and no excessive intentional watering).

Even having soil perched above the water is no guarantee if you have a wicking (water conducting) material in contact with both the water and soil, without a wicking break. A wicking material with no break will constantly siphon water to the soil, attempting to achieve osmotic equilibrium.

Unless you are willing to live with a bog, you need to demolish the current island and, if you wish, rebuild it. My advice would be to build on a foundation of Matala or some other non-wicking material. If you want to achieve a less-unnatural appearance around the margin you could easily carve the Matala margin into a nice shape on a bench top, and then (for example) take some fiberglass window screen and coat it with fish-safe epoxy putty, which will both fill and adhere the screen. Color the putty with nontoxic dry pigments. Then get some black fish-safe silicone cement and adhere the Matala to the (well-cleaned) tank bottom.

Anyway - there's some thoughts. Good luck. Learn from this experience, and make it have value to you. Don't let it just be a damned waste.
 
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