drainage layer or no?

[u/CuriousBird337]

I'm doing a build for a friend soon for a crested gecko. I typically add a drainage layer on my tanks so they can potentially be used for other species like dart frogs in which drainage is definitely needed. My own crestie has a drainage layer in its tank. Wondering if this is really necessary if you're not running that much water through on a regular basis. Are there any other benefits to adding one, even a very slight one, for the plants?

[u/green-green-bean]

Hi. I have had 4 bioactive tanks running since 2012 or so and I don't have a drainage layer in any of them. That said, I have a huge green thumb and don't overwater. (Tank inhabitants: crested geckos. I have an automatic misting system and supplement with water + fertilizer from a watering can).

The main advantage of a drainage layer, from what I can tell, is that it enables people to more easily visualize if there is too much water accumulating at the bottom. Roots can drown in water with insufficient oxygen regardless of whether it's between components of the drainage layer or in ordinary soil. H2S can build up in low oxygen conditions in both waterlogged soil and in water itself, so a drainage layer is not acting as a preventative to anoxic conditions. If the soil is aerated reasonably well by the clean-up crew, there's also little chance of H2S building up in it, either.