Temperature
Temperatures for egg incubation vary in the reptile world. Each species will have their own best points or guidelines, so it is essential to research this before you buy an incubator.
You will need to ensure that your chosen incubator can select this temperature range – some can go from between 2C to 60+C in degree increments, but some only have a choice few settings which may not suit those animals which have to have very low or very high temperatures.
Humidity
Each egg-type will have to have a particular humidity to ensure both the heat is regulated and that the egg doesn’t become too dry.
If you need high humidity, you will need an incubator which specifically mentions this as a key feature and has a tray which you can fill with water or something similar. Dedicated incubators for certain animals will also vary in how much humidity they can handle – snake incubators are best for humidity, for instance.
Lizard eggs need very high humidity too, as they breathe and sweat through the pores of the shell. But too much moisture can result in mould and bacteria in the egg and incubator.
You will need to check that there is a good seal around the doors, any glass and at the edges. 75% is often a good standard marking point for many reptiles. Anything below 50% is dangerously low, and anything above 90% can cause bacteria to spread like wildfire.
So, check the ideal temperature and humidity for your eggs before you start the buying process.
Size
There are three things to keep in mind here. 1) You want the incubator to be big enough to house all of the eggs and 2) it needs to be the right size to fit into your home. Number three is being the right size to house the size of the eggs.
If you knock it when going past or have to move it, it risks the eggs inside. If you have an animal with large eggs, the chosen incubator will be unable to house as many as these as with smaller eggs.