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Choose your Incubation Substrate.

The choice of your incubation substrate is an important one and which is best is a hotly debated topic. The most commonly used types are:

  • Organics
  • Vermiculite
  • Perlite
  • Hatch Rite™
  • Superhatch™


These consist of peat, moss, coconut fibre, soil and other similar media. The problem with these is that they all hold copious amounts of water near the surface which keeps the eggs "wet". This can lead to all sorts of problems like mould and bacteria growth. Also sterilising it is very difficult necessitating purchasing more of it every time. It doesn't tend to come pre-sterilised either for most of the types and thus bad moulds and bacteria and parasites could already be in it which will thrive in the incubator environment.

They have their uses but for me - not for incubation.


 Vermiculite is a natural mineral that expands with the application of heat. The expansion process is called exfoliation and it is routinely accomplished in purpose-designed commercial furnaces. It is a limited expansion clay with a medium shrink-swell capacity.

It has been used for absolutely ages in the reptile industry but it requires strict moisture management to get the benefits from it. It tends to get clumpy and sticky when wet - hold moisture well but at the core of the substrate will tend to clump together and not release moisture efficiently as a vapour near the surface. The surface area tends to dry out more than the rest over the duration of incubation but it does have good wicking properties. Moisture content of the substrate has to be carefully monitored with a suitable regimen and weighing scales to ensure that the environment doesn't dry out too much. Sterilising it after use is extremely hard to achieve - but it's so cheap that replacement is the best option. It is fairly sterile when you receive it in the pack. It goes slightly darker when wet but colour change is not a great indicator of moisture content.


I used it myself for over a year but like I've mentioned already it does require a strict maintenance regimen to get the best from it. It would dry out too fast on occasion until I got the hang of using it. Recommended but there are better alternatives.


 Perlite is an amorphous volcanic glass that has a relatively high water content, typically formed by the hydration of obsidian. It occurs naturally and has the unusual property of greatly expanding when heated sufficiently. It is an industrial mineral and a commercial product useful for its light weight after processing. This commercial heating expansion process leaves it with a great surface area and akin to a hardened sponge. It has the ability to absorb a great amount of moisture as a result.

For incubation it gained lots of popularity over the last 10-15 years and is probably now the most used medium for incubation worldwide. It doesn't wick which is a good thing but releases it's moisture gradually over time as the result of warming - which is what we are after. It resists condensation occurring, because it is effective in holding it's moisture in it's cells - thus its great for guarding against mould growth. A good ratio of Perlite to water is 10:8.

  The single drawback to this otherwise ideal substrate is the fact that it's white when wet and dry and very difficult to tell when it has lost an unacceptable amount of moisture during incubation. It needs efficient regular monitoring and weighing to ensure that it doesn't dry out too much. Many breeders compensate against this by not having any ventilation holes at all in the Perlite egg container. Opening the container once a week for oxygen exchange. Another peculiar problem with Perlite is that when it dries out enough to cause dessication of the eggs it tends to make the eggs collapse on the underside - meaning you have no visual clues as to the eggs health until you pick it up - which as you know is not advisable.

Another disadvantage is that it is fragile - it will eventually break down into a powder if handled regularly - I liken it to coral in that respect. It can be sterilised but it's difficult as it floats so boiling is out. It's cheap enough though that replacement is the best solution.

Hatch Rite™


This is a relatively new player in the substrate field. It doesn't reveal it's ingredients on the packet but breeders suspect it contains Perlite and some form of water retaining gel. It comes ready watered for immediate use in a sealed bag.

It's only drawback is that you cannot gauge how much water is in the product to start with. It's a good product and ideal for the infrequent breeder - Not much more expensive than Vermiculite or Perlite.

Difficult to get hold of in the UK.



 This is a fairly new product from Alan Repashy in the USA. It's made from Arcillite. Arcillite is a calcined form of Montmorillonite a substance that is common throughout the world and goes by other names. Calcination (also referred to as calcining) is a thermal treatment process applied to ores and other solid materials in order to bring about a thermal decomposition, phase transition, or removal of a volatile elements. For example some people believe that Superhatch is crushed up clay pots that are then re-fired at approx 1200ºC to remove unwanted constituents.

It is a very common component for Bonsai tree growers because of its excellent water retaining properties. It's that good at it NASA use it for their plant growing experiments in space. The pores are very small compared to the other media and this helps lock in the moisture and release it much more gradually. It's other great advantage is that it changes colour to a dark brown from it's very light tan colour so is a great indicator of moisture content. When wetted at first it's ratio of weight to water weight is approx. 1:1. it's hard and tough - doesn't break down and being heavy can be boiled for reuse. Unlike hatchrite™ it doesn't contain any artificial water retaining gel.

Sadly - this seemingly perfect incubation medium is Very hard to get hold of in the UK. sad


 I wanted to try Superhatch but could not find a supplier anywhere in the UK. It seemed to me to be just what I was looking for in an incubation medium. So I did a bit of research. Now, Bonsai growers are fanatics - just like we are about our Geckos! So I looked there first. Do these guys use alternatives to Arcillite themselves??

Arcillite is used as an alternative to akadama in the bonsai world but both are expensive so do these guys use anything else that  they have discovered has the same properties?? Turns out they do indeed!

Again, these products are all (basically) clay granules that have been fired/heated to create small pellets or granules that are water retentive, extremely well draining and are stable, that is they will not breakdown readily. These guys use something called diatomaceous earth/diatomite as an low cost alternative. So what is it?

Diatomaceous earth consists of fossilized remains of diatoms, a type of hard-shelled algae. It is used as a filtration aid, as a mild abrasive, as a mechanical insecticide, as an absorbent for liquids, as cat litter, as an activator in blood clotting studies, and as a component of dynamite. As it is also heat-resistant, it can be used as a thermal insulator. Diatomite is also used as an insecticide, due to its physico-sorptive properties. The fine powder when dry absorbs lipids from the waxy outer layer of insects' exoskeletons, causing them to dehydrate. Bonsai enthusiasts use it as a soil additive, or pot a bonsai tree in 100% Diatomaceous earth. Like Perlite, vermiculite, and expanded clay, it retains water and nutrients while draining fast and freely allowing high oxygen circulation within the growing medium.

So basically it has exactly the same properties as Arcillite when in a calcined form, which is how it's commonly provided.

I wanted to try some of this so where could I get this calcined clay from? You'll never guess ---

tescos premium

That's right - Tesco's Cat litter - Tesco's Premium Lightweight cat litter is a 'Moler Clay' and originates from Denmark, exported by a Scandinavian company - Damolin. Moler Clay is a type of Diatomaceous Earth or 'Diatomite'. 

By the way another brand of cat litter that has exactly the same properties is Pets at Home's Sophisticat cat litter - it's exactly the same stuff!

So how do I use this stuff then?

Firstly I thoroughly wash a batch of it in a sieve in the kitchen sink to get all the dusty residue off of it. I do this until the water runs almost clear. I then leave it to drip dry for about 10-15 minutes. My experiments showed that it absorbed an equal amount in weight of water after this process -- a ratio of 1:1. If you require a smaller amount of moisture then let it dry out a bit first and then spray water back onto it until the correct ratio is acquired.

I then get hold of a cricket feeder tub. I leave the micro slits in the side and create 4 more 1-2mm small holes in the lid. Because this stuff absorbs so much water initially I noticed that it was almost too water retentive - so I wanted to create the perfect humidity requirements for the eggs by allowing the moisture to escape naturally through the honeycomb structure and out of the lid. Because the vent holes are literally so small what I get as a result is a constant stream of humidity on the eggs as the vapour passes them from the substrate and gradually out of the holes and slits. The moisture is released very slowly by this stuff. As the outer window of the Herp incubator is exposed to the home environment the inner part of it does suffer condensation - but most importantly the containers and the eggs do not suffer any condensation at all - they just have excellent level of humidity 24/7. When measured it was 80% which is practically spot on!

Maintaining the water content is even easier -I simply weigh the total amount of the container, litter and water; and mark it on the container with a permanent marker. I do not monitor it for the first 2 weeks. Every week thereafter I weigh the whole lot and if it's dropped 5 grams I add 5 grams of water via a syringe near the edges. Handily 1 ml of water weighs approximately one gram - so 5 grams is 5ml from a syringe - simple as that.

Once a week I open the incubator - open all the lids and allow some fresh oxygen exchange - this also allows the stagnant moisture vapours to expel a bit. - The water goes stagnant in ANY medium you use. That's all I do - so far this year - 100 percent hatch rate with nice 4-5 gram hatchlings in perfect health.

Each cricket tub holds four eggs. When the fourth egg hatches I throw away the medium into the kitchen bin and then wash out the cricket tub for the next batch. This stuff is so cheap there is no need for sterilisation to re-use!

This has been my secret medium for over a year - well I wanted to test it first! And now I'm releasing it to you the public. I "think" I'm the first to stumble upon this alternative to Superhatch - but saying that I know I have doomed myself to being told that I was not! If it turns out I am - then give me some credit people! Nevertheless - enjoy my discovery!


F. Passaro

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