Andrew| January 6th, 2020
DIRT! (and also other substrates). This is a topic about dirt, so buy a couple of bags of top soil, roll up those sleeves, and lets get dirty! There is a lot to cover on this topic, and this article is by no means a complete one. We will try to add, update, improve, explain and expand upon this article as time goes on.
In examining this article you will find a preamble being mostly ramblings from the author (this and the next few paragraphs), a breakdown of several commonly used substrates, a few soil mixes that have been found to work very well and finally a few different definitions and sub-topics that are pertinent to the article. Now, with out further ado, lets talk dirt!
Substrates are a very important part of setting up an enclosure. It is likely the main component of an enclosure that most animals will come in contact to and therefore should have a great deal of consideration put into it. There is a lot to consider when choosing a substrate for your reptile. Here are a few important ones to consider before diving in;
This article will attempt to cover several different varieties of common enclosure substrates including pros and cons as well as offering a few recipes that work well for things like bioactive. We will also discuss, in brief, topics such as plants and clean up crews that are necessary for bioactive to operate properly (see full topics on these subjects for more details).
One final note, as this is an attempt to be a comprehensive coverage of the most commonly used substrates, there will be substrates on this list that are not recommended for use. Please keep this in mind while reading through. At the end of each topic, there will be a quick opinion statement of each substrate.
Calcium carbonate, often made from ground aragonite. This product is highly discouraged. It has a relatively high ph and can form into a paste when wettened.
This product is claimed to be completely digestible and great at aiding in calcium supplementation, but in reality, it is a huge risk to your animals’ health.
This is probably the most discouraged product found on this list. It is highly dangerous and does not benefit your animal in any way.
“Soil lite” Coir is a very good option as it is a fine particulate that can absorb a decent amount of water content before it becomes soggy. It is very useful for regulating humidity within an enclosure. Coir is often available in a fine, ground state and often pressed into “bricks” which can be rehydrated with water
(Tip from the writer: Using half the water recommended and waiting longer will allow you to prevent your coir from being so soggy once expanded. Just leave it overnight and then add a bit more water as needed. Just try to have as much of the brick in contact with the water as possible when starting).
There is also a less processed version, usually called coco chips. It is not exactly coir, but is a good option if you would like to offer larger particulate to your substrate, but this topic will mostly cover the pluses and minuses to the fine coir. As stated below in the mulch section, many mulches are pine based, even in the reptile trade. Coco chips add larger bits that retain lots of water but still allow for the drainage benefits of larger particulate in an enclosure without the follies of pine-based mulches. It would likely be best used in conjunction with other materials but can be used on its own.
Coir is made from the outer hull of coconuts. It is ground into a fine mulch, similar to the size of coffee grounds. The composition of this husk layer is incredibly fibrous and flexible which is the reason that coir can sponge up so much water. It is available from many sources, but the reptile specific brands tend to be the safest option, although often a bit more expensive than horticulture versions.
A final benefit, or downside for other reasons, is that coir is very nutrient poor. This makes it less beneficial to bacterial and fungal growth straight from the store. This does though mean that plants have a harder time thriving in coir alone. There are microorganisms and fungi though that tend to thrive in coir so this isn’t a guaranteed benefit and sanitisation is still recommended because of this.
Coir makes a very good soft substrate. The risks involved with this substrate, although still possible, are much less likely than with other loose substrates. If you want to try out a simple loose substrate, this is one of the best options. It is very versatile for use in nearly any environment.
Mulch makes a decent substrate option for many reptiles. There are many different types that can be purchased. It is important to make sure you are buying something that works well with the enclosure you are putting together. Aspen is often very good for arid setups while most other options are good for semi-arid to tropical.
It is very important when choosing mulch to make sure you avoid any type of pine. They contain resins which can leach out and harm your reptiles. Mulch often works best when combined with other components such as soil or coir.
Mulch is not a terrible option, but tends to be best used in conjunction with a finer substrate like topsoil or cocnut coir.
Paper towels are a good alternative to the simplicity of repti carpet, without all of the problems associated with it. They are easy and clean. Maybe a bit drab or sterile in appearance, but very effective in many applications.
Paper towels are a very good choice for many applications. They are a good substrate option, but there are often better, more permanent options available.
A lot of beginner enthusiasts will be tricked into using reptile carpet felt liners. It has the potential to be a decent product but is much more likely to be a harborer of bacteria. We recommend keeping away from this stuff!
We do not recommend using Repti Carpet. Paper towels are a much safer and better option for any application that repti carpet may be considered.
Many animals that live in arid environments have been slapped with the misconception of living solely on sand. While many of these reptiles do occasion or even frequent sandy areas. The likelihood of them living completely and even dining on a sand surface is quite unlikely. The likelihood of an insectivore finding a plant-eating insect crawling out on hot, barren sand is much less likely than that animal climbing into a shrub and picking it off of a branch or from a thicket of grass or brush. In addition to this, most sandy environments have much finer and or smoother particulate than the commonly used sand; playsand. Playsand is often comprised of crushed and ground sandstone. There is little time for processing this sand into something super fine and smooth when the process used to make it is pulverizing.
For example of the types of sand animals are accustomed to, in many areas that Bearded dragons live, if sand is involved, the particulate is very likely comprised predominantly of fine sand and what has been coined bulldust; super fine sand that is small enough to be swept into dunes and flats that cover harder packed ground underneath. Another example may be reptiles living on or near riverbeds. River sand, albeit often varying in size is more likely to be much smoother due to erosion over time.
For a more “scientific” perspective in regards to sand; all sand content comes in varying sizes. No scoop of sand will be uniform, but fine, arid sand tends to range in size from 2-100 microns where crushed sandstone playsand tends to range from 150-480 microns.
One final note about sand. Most sands are not transported very far due to costs of shipping and availability. Your local sand may be drastically different in size, quality and composition to another area. The composition of sand, in general, is so vastly different from place to place, that it is difficult to cover all types. The pros and cons section of sand will generalize sand as a whole but lean towards describing the benefits and follies of playsand as it tends to be the most commonly used option.
Sand on its own tends to be a dangerous gamble. It is often used best in tandem with other substrate options. If you wish to use a loamy substrate, please check out the soil mixes below. They would likely suit your needs much better.
Soil on its own often makes a perfectly acceptable substrate. The big issue comes in the fact that it can be quite messy. Expect your animal to have muddy spots on them and all over their enclosure. A bowel movement or a tipped water bowl can make a huge mess. Most keepers steer clear of soil on its own because a mix can often be used to offer a finer substrate that is less messy and more suited for an animal’s needs.
The important thing to know with soil is that you must get organic soil. Pesticides, fertilizers, supplemental chemicals, foreign objects, and much more can be very dangerous to your animals. Additionally the source of many soils can be very questionable. Some companies make rich topsoils by flooding fields with sewage or animal waste and allowing it to decompose and turn into a usable product. This bio-sludge can be quite harmful. Because of all of the above, purchasing organic, sanitization and processing is always recommended.
Some soils are also incredibly loamy or full of clay, which are components of soil, but too much will make your soil difficult to work with and be too nutrient poor.
(Writer’s note: for my uses, I normally stay away from clays as they don’t often serve a useful purpose in my soil mixes. They would offer more hold for things like burrows, but often raise how messy your soil becomes.)
As a final sum-up note, a little extra work makes a much more optimal substrate than soil alone.
Albeit messy, soil can make a decent substrate. Most will find that it is easier to add soil into a mix than use it on its own, especially because of knowing more of what is in your soil mix, even if a part of that is the wildcard soil.
This is a vast topic. There are a lot of different options, some better than others. The majority of the remainder of this article will cover different soil options. As for the general pros and cons of soil substrates:
We are about to go into a much more lengthy explanation of soil mixes. In general they are a very good option, but often take more care and additions to operate properly. It might not be the best for your first enclosure build, and a better option for adult reptiles once they are less prone to impaction, but soil mixes are a great choice for keepers ready to branch out into naturalistic setups.
Tile is a very nice option, especially for arid species. It does not offer much in the way of helping with humidity, but it is great at retaining heat and easy to clean. Many keepers will use tile pieces in basking areas even if their substrate is a different type. ( This topic is predominately for earthenware tile. Some points below do not apply to vinyl imitation tile, but many do, even if just partially)
Tile is a very good option under most circumstances. It is expensive in comparison to most other substrates, especially considering linear verses cubic coverage, but is still often quite inexpensive.
There are many options out there when it comes to soil substrates. In the pet trade, most companies have their own jungle, bioactive, ABG, tropical mix. It all often tends to be fairly similar with only slight changes to composition; being additions and or subtractions of content that the manufacturers believe are necessary. With that in mind, many are vastly more expensive per equivalent volume than others. Some for good reason, others because the packaging and logo are pretty (Writer’s note: I’m looking at you Lugarti).
With that in mind, not every soil mix is made equal. Some will even contain components that are arguably problematic. As an example, components such as calcium/sodium bentonite will be included in loose soil substrates. Bentonite, in its multiple forms, makes up a large portion of Excavator Clay (by Zoo Med). Bentonite is a clumping agent found in many products such as medical, construction and even kitty litter. In small quantities, it can serve an important and safe role, but in larger quantities, it can wreak havoc on the body. Excavator clay, in its correct application, is to be hard once shaped and dried. Some loose substrates have bentonite in their composition to help it hold shape. Bentonite acts like silt and can cake into an animal’s gut under certain circumstances if ingested over time. It also absorbs water from the body.
It is important to do as much research as possible into a store-bought mix to know exactly what you are buying. The likelihood is even with the inclusion of a problematic component, there is not enough of it to truly be a threat, but always something to consider, especially given that other comparable products may not include it.
If you have made it this far, thanks for holding out! Here are a few options you can do on your own. Like other options previously mentioned, they all have their place. Some work better than others in different conditions.
A simple mix of two of the above substrate options. It is often recommended to do a 1:1, 2:3, or 1:2 ratio sand to coir. This mix is great at retaining moisture and wonderful for burrowing animals. It will hold small burrows, but for a medium to large animal, there may need to be some additional structure like large rocks to help hold this substrate up. This substrate still has the issues of the two substrates as described above, but tends to be safer than sand alone as the coir is much easier to pass and will help move along any ingested sand. (Writer’s note: this is the only time I would recommend using a moderate amount of playsand).
This composition is a nice and easy mix for bioactive builds. Topsoil contains a lot of organics and the mulch allows for slow decomposition, ease of digging and aeration of the substrate. To an extent, the less mulch you include, the more likely burrow retention will be capable, the more mulch you include, the less of a muddy mess you will have. Your terrestrial animals will likely become quite dirty from this setup though. If it dries out there will be a lot of dust, if you let it get too wet, you will have a boggy mess. Recommendations are 1:2, 1:1, or 2:1 in respects to what has been aforementioned. If you want a less rich and/or more sterile blend, swap the top soil for coconut coir.
“Jungle mixes” are great for plant growth, microfauna, and naturalistic builds. There are benefits to setting up a bioactive enclosure, but with these benefits come more responsibility; watering plants, moisture gradients, plant and soil maintenance, etc. This mix is comprised of eight items. All are recommended, but all or some of the final four can be removed for simplicity.
(Writer’s Note: This is my mix formula. It is not incredibly nutrient-rich, but will have a slow leach of new nutrients from the decomposition of the leaves and mulch. It at least partially relies on nutrient supplementation by the animal and cleaner crew that live on it. Plants should do just fine as long as they are not incredibly demanding ones. I have grown pothos, fittonia, inch plant, ferns, sedum, moss, and others on this soil without the need for nutrient amendment.)
4pt Eco Earth
1pt Leaf Litter Crushed (Magnolia, live oak or most hardwood)
2pt Organic Top Soil (bonus points if you mineralize it (see below))
1pt Orchid Bark, Safe Mulch, or Coco Chips (aids in draining, nutrients, and texture)
1pt Pearlite (aids in draining and aeration)
1pt Sphagnum Moss (shredded fine to avoid swallowing long strands) (aids in moisture retention)
2pt Peat Moss (adds acidity and moisture retention)
Bugs, plants, and dirt. It’s that simple or that complex! Bioactive builds allow for the breakdown of organics, such as waste inside an enclosure. This reduces the need for cleaning, regulates humidity and promotes a more realistic enclosure setup through microfauna and plants. Bioactives do best when the cleanup crew has spaces to hide and things to climb on to get off of the ground on occasion. A humidity gradient is also a great addition as long as your dry side is not where your tropical plant is trying to grow.
This will likely be covered in more depth in another article, but clean-up crew covers a wide variety of inverts that help to keep enclosures clean. An important aspect to cleaner crew is that they do a good job at cleaning up what you don’t want (waste and dead plant matter) while leaving alone what you do (your plants and pets). Another benefit of most cleaner crew is that their numbers will fluctuate as food is available. Just keep this in mind if you believe that they may not have enough food to support their numbers. Three that are great additions to enclosures are:
Rollypollies! These are your macro cleaners for tropical to semi-tropical builds. These little crustaceans (You heard me right! Not bugs!) love decomposing plant matter and animal waste. They can take out quite a bit of waste as their population rises in an enclosure. Isopods range vastly in variety. Many specialize in different purposes, I.E. size to avoid predators, speed of reproduction to combat being easily eaten, better camouflage, burrowing, higher desire for protein-based foods, arid adaptations, etc. Isopods require some form of a water source to occasionally hydrate their gills. This can be a water bowl, damp soil, wet moss, etc.
Springtails are often smaller than a grain of rice. They make up the most readily available micro cleaners. Where isopods break down waste and matter, these little inverts break it down more. Springtails eat superfine waste, starches, sugars, microbes, and especially fungi. They are an amazing defense against molds when their numbers are decent. Springtails require some form of a water source to occasionally hydrate their bodies. This can be a water bow, damp soil, wet moss, etc.
AKA Buffalo Beetles. These little guys are in the same family as superworms and mealworms, but they have one really useful attribute that the others do not. They are only interested in dead things. They will not pick on your living animal but will clean up after them. They are also quite small and very capable of cleaning up messes. A very nice trait of these little insects is that they take in most of the water that they need from the food they eat. They do very well in arid to semiarid environments.
For a quick definition, mineralization is the process of breaking down organics into inorganic nutrients using microbes, oxidation, and brief aerobic immobilizations. It differs slightly to decomposition in the fact that mineralization is solely bacteria removing organics, where decomposition is often a combination of physical, heat, chemical and/or biological breakdown of organics into easier to process organics and some inorganic nutrients. It is also often the result of different conditions causing the breakdown process. Often, mineralization is a secondary step in processing organics past decomposition.
The process is a lot easier than the definition. It is often used in the aquascaping trade to break down soils into more optimal nutrients for plants while avoiding the addition of nitrates nitrites and ammonia from the decomposition of the organics found in said soil. It is a good option to employ when making soils for plants as well as it will turn your soil into mostly pure nutrients which helps to inhibit fungus and algae growth. There are online resources that recommend soil mixes to make prior to beginning the process for even more nutrient-rich mixes, but topsoil or garden soil on its own should do just fine for our purposes. The draining process and mineralization should also help to get rid of any fertilizers or chemicals found in your soil.
The process involves placing soil into a container, the wider, the better (Air contact is key. You can even use a tarp for the drying process if you would like). You will go through the process of adding dechlorinated water to the soil and flooding it, then draining the mix, trying to lose as little soil as possible, and allowing it to slowly dry over several days to weeks stirring the soil on occasion (this is when the mineralization happens). Once the soil has become fairly dry, you will start the process over again.
Once nearly, fully mineralized, the soil should be quite grainy and have next to no smell.
It is best to take plants out of their current soil, rinse the entire plant and sanitize with a bleach or F10 solution and rinse again before adding them to an enclosure. This reduces the chances of adding fertilizers, chemicals or pests to your enclosure.
One thing that is very important when putting together a substrate is to avoid as many foreign dangers as possible. The best way to avoid this is to purchase organic and or reptile specific products. Physical, chemical, and microbial contamination to an enclosure can all be deadly;
As for sanitizing, several recommended options are:
There are a lot of different options out there on how to do this, but the important thing to keep in mind is that you want to reach a temperature of approximately 170 degrees Fahrenheit (Approx 76 Celsius) to kill anything living in your substrate, hardscape, etc. An easy way to do this is to bake your item at 250 F for 2-4 hours. This also greatly reduces the chances of a fire from baking at higher temperatures. There are fungi spores that can survive up to 250F, if you want to avoid everything, a 250 F internal temperature is advised, but you should have roughly an 80% chance of fully sterilizing your substrate at 170F.
Most microorganisms and especially fungi will not survive below freezing temperatures. An internal temperature of 32F (0C) or lower should efficiently kill most pathogens. Some bacteria and organisms though are capable of going into a dormant state to survive. They will not reproduce or thrive while in their dormant state, but can continue to live and multiply once they have reached more optimal temperatures.
This works better for hardscape objects. For anything that does not fit in an oven, F10 or a diluted bleach mixture should be used to saturate your item needing to be sanitized. Allow the object to then fully dry. This should allow the F10 to become inert and all chlorine in the bleach to evaporate. It is then best to rinse the object off and allow it to dry a second time before adding to your enclosure. The downside to this process is that it is only a topical cleansing and does not fully sanitize internally.
Boiling an object works well for large pieces and substrates. Add them to a pot of boiling water and let sit for at least 15 minutes. A large pot and turning long objects often get large pieces that would not fit in an oven. You can also pour boiling water over objects, but you may risk not thoroughly heating it. Boiling can be damaging to many items. Even wood and rock can deteriorate/crumble.
Similar to boiling or baking, but you can place an object into a pot and wrap foil or cover the top. Allow the object to steam for 30 minutes to an hour to ensure proper heating. You will get all of the benefits of boiling, but steam heat is often more forgiving than boiling water.
Writer’s note: You made it to the end! I hope this all was very useful. If you have any questions or suggestions, please feel free to let us know!