Do you think some sort of dry clay component could/should be added to leopard gecko substrate? I was researching soil content in iraq and found someone's college thesis, and it said that it contains a top layer rich in calcium and magnesium with humus, but is comprised overall in order of most to least of clay, limestone, siltstone, and some other stuff
Many people use that! If you use quality decomposed granite, a small portion of it will be clay (granite that has been weathered to a very small particle size). Other people use Excavator Clay or other clay as an ingredient.
However, in an enclosure, we can’t use a bioactive substrate that is extremely high in clay, as it would create drainage issues in the small space. Clay soil is dense, since the particle size is so small, and becomes very heavy and packed. When moistened and then dried it becomes very solid. Water will not filter through it.
In the wild, when it rains heavily in a clay-rich desert area, there are flash floods. Water flows along the top of the clay soil rather than through it.
Clay also holds a great deal of moisture in it for a long time when insulated from the heat by substrate above it. In the wild, this is great, because the surface of the substrate (looser and humus-y) will allow the water to drain through and become dry, while the clay underneath stays moist (and cooler) long, long after the rains have stopped. This allows animals to self-regulate their humidity needs by burrowing or using other animal’s burrows to reach that moister layer. Not only do reptiles take advantage of this, but so do mammals. Check out kangaroos!
However, in the arid vivarium, that’s not possible. Our substrate isn’t nearly deep enough to provide this natural gradient (and most have a solid bottom underneath), so we create artificial ones, by using humidity-holding substrates in pockets that we can moisten. If we attempted to mimic the actual desert substrate in miniature (”in shallow”), it would rot the roots of our succulents, and create a waterlogged, too-humid environment for the desert species.
Instead, in our small space, we need to use a quick-draining substrate so that water doesn’t pool. We do that by using larger particle size mineral ingredients in organic material. That includes decomposed granite, large particle calcined clay (non-absorbent fired clay pebbles), sand, volcanic rock, and so on.
However, a low proportion of clay is definitely a possible part of an arid bioactive substrate. Before you use your mixture in your enclosure, you should wet it and then let it dry, checking for drainage, that it doesn’t get dusty, that it holds burrows, and that it doesn’t pack when dried out. Proportions can be adjusted, and then the substrate can be checked again.
For those who don’t want to go bioactive, and don’t like the look of tile or paper towel, Excavator Clay is a safe and easy substrate choice that has a pretty neat look. As leopard geckos come from an area with packed clay soil, particularly rocky areas within its range, it’s a good choice.
It is actually meant as a solid substrate. You moisten it, sculpt it in the enclosure, and then let it dry, which creates a hard, solid substrate. (Reptiles should not be added to the enclosure until it is completely dry.) This demonstrates how solid clay will become! It can be re-moistened to re-sculpt or remove it. Burrows and hides can be formed directly into the clay, and decor elements can be built in (like rocks, wood, and fake plants emerging from the clay).
Because it is a solid, thick substrate, UTHs can’t be used under the enclosure. The substrate -- or even the glass -- can crack. Some people use tile over the UTH and Excavator Clay in the rest of the enclosure. Otherwise, you can use overhead heating, like an RHP or CHE.
Maintenance includes cleaning up poop and urates, which can mostly be swept off the hard clay. In many cases, however, urates will soak into the Excavator Clay so parts may need to be replaced often, unless it is possible to build in or include a non-absorbent surface where the leopard gecko poops every time (such as a Lizard Loo, rock, or tile). Some leopard geckos poop only in corners, so this is possible.
In addition, the substrate should be checked to make sure no parts are becoming dusty or crumbling.
Also, any humid pockets in the Excavator Clay (such as borrows to be used as a humid hide) need to be lined with a waterproof material, as the substrate will break down if it gets wet.
And my usual warning, because silicosis is no joke -- be careful handling any dusty mineral material, including dry clay, and when using it with a reptile. Silicosis is damage to the lungs from inhaling silica particles, and it is accumulative, meaning breathe a little now and a little later, the damage keeps happening. There is no cure, and only supportive treatments.
