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Hi, I set up an Exoterra 18x18x24 vivarium a few days ago. Pretty standard set up (as far as I can tell - all new!) bedding in for at least a month before a frog will cross the threshold.

2" of hydroton, drainage mesh, 1.5" of ABG ramped up to 3-4" at back, leaf litter on top, half a dozen plants, cork branches, small water bowl, isopods and springtails

Although there's a lot of hours of reading websites and forum posts, YouTube watching and a rookie mistake or 3 underlying what's written above! And plenty more of all of those to come, I'm sure. Getting there though. I think.

One thing I'm not sure about: I gave the plants an initial light watering in, and have been misting everyday. The substrate is moist around the plants, pretty dry elsewhere that I can see through the side of the viv. There's no water in the bottom of the drainage layer, except a bit of condensation when I've recently misted it. I've read in places that a layer of water in your drainage layer helps with humidity, but that you should drain some off if it gets past halfway towards the substrate layer (I've got one of the Exo tanks with the drain and the tubing to a tap.)

Should I get the mini watering can out and water through the substrate until I've got a bit of water at the bottom of the drainage layer, or should I just keep misting and let it build up over time?

I've read that over-soggy substrate leads to lots of mould but not sure if it needs an initial soaking when you first set up or not and haven't managed to find anything that talks specifically about this. Advice gratefully received!
 

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I disagree.
You should have water in the drainage layer, up to 1"-0.5" below your mesh that separates the soil from the hydro-balls. It's not just about a mass of water to stabilize humidity (although that's important) It's about your nitrogen cycle. You have a bio-active environment (sort of, but let's go with it). In order to turn the toxic nitrogenous compounds your animals release (ammonia) you need a functioning nitrogen cycle. And this means you need two types of bacteria: Nitrosomas and Nitrobactor. They both need moisture and a surface to adhere to in order to survive. One, Nitrobactor, needs oxygen in order to oxidize nitrite to nitrate (the non-toxic form that is plant food) The other, Nitrosomas needs an anaerobic environment (meaning no oxygen) to reduce ammonia into nitrite. This happens in the stagnant water in your drainage layer. Plant roots will seek out this layer and drink up. It's like a superfood smoothie to them. This also helps them if the main area of the vivarium dries out a bit. They can draw from the well and save your valuable froggies if the mister breaks, of the room thermostat goes nuts and tried to cook the room. The transpiration of the plants can be a supplimental humidity source and buffer for your frogs living area,along with misting.
I use a 3 layered substrate personally in all but simple grow-outs. This allows for a pure water layer under the Hydronton balls which is half water/half air. And then the final "soil". This allows for a vibrant nitrogen cycle as well as a volume of water to buffer chemical reaction and maintain the Oxidation/Reduction Potential, which is the ability for electrons to flow freely through a system and is the essence of life itself. But I've seen plenty of soil/drainage layer set ups that work very well for years. I'm just kind of a geek.
So get some water into your subsurface reservoir- and then call it the water table.
 
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Nitrosomas needs an anaerobic environment (meaning no oxygen) to reduce ammonia into nitrite.
NH3 to NO2 goes something like (2)NH4 + (3)O2 --> NO2 + (4)H2O + (4)H ions. That's aerobic.

Nitrosomonos is aerobic (though a facultative anaerobe, I just learned). Though whatever genera end up performing nitrification, they're (often) aerobic; there are lots of very efficient closed aquatic systems with no anaerobic zones at all (bare bottom holding tanks with canister-filter type filtration).

Denitrification is anaerobic (bacteria use the O from NO3 and the N2 exits to the atmosphere), but encouraging that process wouldn't be needed in a viv drainage layer. I run a sulfur denitrator on my reef tank, BTW, and it is a neat thing.
 
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Discussion Starter · #6 ·
Cheers gents. Sounds like it won't hurt to get some water into my tank drainage layer (I mean, my daughter's, but I can already tell which of us is going to get steadily more obsessed with this:)).

That's more chemistry than I've tried to get my head round in 30 years! Loving the scope of this new hobby and its potential layers (obligatory substrate pun) of complexity...
 

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NH3 to NO2 goes something like (2)NH4 + (3)O2 --> NO2 + (4)H2O + (4)H ions. That's aerobic.
I want to start by keeping this is super-friendly. I was trying to keep my answer simple and short(ish), but if we want balanced equations, we shall have them. Time for some chemistry fun for those on the forum who dig that sort of thing. This equation above is for the oxidation of ammonium (NH4+) which is the form ammonia takes when it dissolves in water. It is also the denitrifying equation that can occur in those cool sulfur de-nitrifiers, but take several steps in our vivarium's (which are not reef aquariums), Nitrobactor, in our terrestrial environments, can take ammonia on directly and the method of Ammonia oxidation they prefers is:
1) NH3 + O2 +2e- = NH2OH + H20
2) NH2OH + H20 = NO2- + 5H + 4e-

This is obviously an aerobic reaction.

Here's where my short cutting took a turn towards the controversial. Nitrosomonas is an anaerobic bacteria, but their nitrogen cycle reaction is aerobic (go figure- damn life forms having complex life cycles and metabolisms!) They perform Nitrite oxidation (and I did say reduction- I was wrong) thusly:

NO2- + 1/2 H2O = NO3-

Simple and elegant. What I had left out in my rush was the final stage which is exemplified in Socratic's equation- de-nitrification. We can run our cycle in an ecological balance as long as someone can consume each by-product in equal proportion. In marine set ups they often balance the equation with "Nutrient export" they grow algae with the spare nitrogenous compounds and then harvest it to remove excess nitrogen from the system. We do the same when we prune our plants. But, eventually, we will need to "get rid" of some of the nitrogen that comes from the food that the frogs eat and poop copiously about. That's denitrification- the final release of the nitrogen back into the atmosphere.
This is done by the anaerobic bacteria's such as Pseudomonas and IS and anaerobic reaction.

2NO3- + 10 e- + 12H = N2 +6H2O

So, just like composting, both aerobic and anaerobic reactions are needed for a complete nitrogen cycle. And a good take away is a bit of a water reservoir in the drainage layer is a good thing. A saturated drainage layer that reaches the soil is a VERY BAD THING. Thanks for making me crack the old text books and not rely so much on the way I remembered it running. Hopefully others will see this as a great learning experience and add another level to the COOLEST hobby out there.
 

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Back to the OP's issue, you most likely installed your weed Bloch upside down and the water is pooling on the lower portions of it. I use fiberglass window screening since this can't occur with it.

Some comments

Ed
 
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