Let’s get the word itself out of the way first. It’s not biotype, but biotope. Because as with most English words we borrowed it from another language, German in this case. So no it’s not a typo.
The definition of a biotope is “...an area of uniform environmental conditions providing a living place for a specific assemblage of plants and animals.” but even that is an awkward way to look at it.
Recreating the wild
Imagine you’re on the banks of a stream, just look at the temperature and humidity as you go from the top of the bank, down to the margins of the water, and out into deeper water. The temperature during the day will likely be higher at the top of the bank, getting cooled as you move further down, and into the water, even there the temperature will probably be higher in the shallows than further out into the channel.
The humidity will most probably rise as you approach the water, although the warmer air up top may have a higher relative humidity. But what about under any plants, there might be a heavy stand of plants part way down, holding the humidity up high, and the heat lower even when the sun is directly overhead.
Microclimates
Each of those locations has a different microclimate. But the environmental conditions are largely the same.
I tend to think of a biotope as a slice of nature. Trying to mimic the ideal natural conditions for the animals I'm keeping, and then make it practical for the vivarium or whatever enclosure I'm looking at. I have no intention of keeping a few thousand bats in an enclosure made entirely of limestone. Instead, I can mimic what they need by providing bat guano and pieces of limestone with an alkaline substrate mix.
Biotopes for Isopods
Asian Tropical Rainforest
Take Cubaris sp. Platinum Isopods - we know they need medium tropical temperatures (23-26 º C) but high humidity (70-80%). The ideal biotope for them is humid and heavily planted. Their natural range is in Thailand, so a great start is looking at the biotope of a rainforest area there.
Start with the soil, writing just over 100 years Robert Troup compared teak and none teak soils, but both were high sand, the main difference being the iron content, so was the soil dominated by a red or yellow sand. The amount of humus was surprisingly low, at less than 5%, and the nitrogen was relatively abundant for a rainforest soil. But he didn't seem to look at the limestone-based soils. If we assume these isopods like other local Cubaris species are found in or near caves then there is an assumption the area is limestone based. That means the soil will have some limestone, although that can be as low as 5% due to the heavy rain. Either way, the soil itself will be lighter and free-draining.
Next the leaf litter. You could go too far and start to try and collect leaves that are only found in the rainforest, but that might be a step too far, instead a decent layer of leaves with a variety of leaf types to allow some choice is best.
Now on to plants. Here is where you can have fun, you can go as far as you want in terms of the biotope. Think of small ferns and mosses to mimic the forest floor, and orchids for their beauty. Maybe some small bamboo cuttings, and don't forget that many aquatic plants will thrive in a high-humidity enclosure.
Humidity and temperature in Thailand fluctuate a fair amount between the dry and wet seasons, so it might be worth mimicking some of that. But don’t forget that in the wild many animals will suffer during the extremes of the seasons, so don’t go too far. Smooth out the rougher edges of the wild to make their indoor life more of a thrive than survive situation.
European Caves
Let's go from the warm humid jungles of Thailand to a cave in the spruce forest of Slovenia. The Stratená Cave system, more famous for the nearby, but no longer connected Dobšiná Ice Cave, are limestone caves that have an average temperature of 4.9ºC, although they do tend to change with the temperatures at the surface, and an average humidity of 95-100%. You wouldn't think of this as the ideal home for isopods, but Trachelipus difficilis has been found at the cave entrances of this chilly biotope.
We’re not 100% clear on what they’re eating in the cave, but the other isopods in there are sampling bat guano, algae and fungi, and probably anything else they can get. Being petricolous, i.e. rockdwelling, these are found on the walls of the caves, rather than the debris on the floor.
Creating this sort of biotope is tricky, to say the least. There aren't really enough studies on this rather secretive isopod to be able to give you any definite ideas. But luckily we have a second species of Trachelipus that we sell T. mostarensis. This species is found across Bosnia and Herzegovina and Croatia.
Trachelipus species are generally adaptable and easy to care for, meaning that the extreme environments we see in the Stratená Cave system are probably at the edge of what the isopods can thrive in, rather than what they need.
Start with the rocks that they seem to prefer. Stratená Cave system is a karst system, so is limestone where the water has worked its way through to make rivers, sinkholes, caves and more. Think about getting some large pieces of limestone for them to live on. You could make the entire inside of the enclosure look like limestone to mimic the cave system. You won't have much in the way of plants, although it's worth adding leaf litter, mosses, and even try and encourage algae on the walls. Keep the humidity high, and the temperatures are fine at room temperature, even in a cold room, although don't allow them to drop too low. We know that no species of isopod are found in the ice cave itself, implying that the temperatures in there are too low.
As to food and substrate, some bat guano, algae-based fish foods, and a basic substrate including moss, powdered limestone, and maybe some sand will be correct for the biotope. Use muted lighting and plenty of places for them to hide out of the light. To maintain the high humidity you will need reduced ventilation, but be careful of allowing moulds to build up.
If you want to add something else to the enclosure look at growing some species of mushroom, or move the biotope just out of the cave entrance to the start of the spruce forest. What plants and flora will you find in that sort of location? It's worth doing the research to find out which of the hundreds of options suits your setup.
Semi-Arid Grasslands
Finally, let's jump from the high-humidity caves to the lower-humidity areas of Montenegro in the Balkans. Klugii Pudding Isopods are ideal for so many vivariums and terrariums as they can take much lower humidity levels than other species, as low as 40-50%.
Whilst this individual morph have a reduction in the red colouration across their carapace, Armadillidium klugii in the wild has a pattern similar to the Mediterranean black widow to ward off predators, showing that their ranges overlap. We know that the spiders primarily live on the steppes and grasslands and that these isopods live on semi-arid grassy coastal areas. So that gives us the first starting point.
For substrate think about a very sandy soil, and look at the sort of plants that will make up a grassland biotope in the Balkans. Keep the humidity in the correct range as they can struggle to shed in high humidity.
Reports say that Armadillidium klugii are found in the crevices and under rocks, so consider adding rocks to provide hiding places for them.
Are biotopes worth the effort?
What you do with a biotope is up to you, it can be a challenge to try and find the correct substrate, plants and other enclosure inhabitants to recreate that slice of nature. But it does make it easier that all the inhabitants need the same environmental conditions.