Ventilation is an aspect of isopod keeping that is unfortunately often overlooked. A popular method to ventilate isopod tubs when first starting out is to use a pin to make small holes around the circumference of a tub. Initially, this works fine with small populations, but over time, as the number of isopods grows, so does their CO2 production. CO2 is heavier than air, and will settle along the bottom, so an apparently thriving colony will suddenly crash and die overnight. The keeper will often insist that “It can’t be the ventilation! They’ve been fine like this for months!” not realizing that unfortunately, it is fine until it’s just not fine anymore.
So, how much ventilation do isopods need? Well, this can vary greatly by species, but it is always better to have too much ventilation than not enough. An important thing to keep in mind is the placement of holes. Holes are best placed around the circumference (sides) of the setup. Holes in the lid of the setup are pointless because they don't encourage airflow. An added negative is baby isopods escaping from nearby tubs can fall onto the lid and crawl through the holes to establish themselves in neighboring cultures. If ventilation holes are only on the sides, this risk is substantially reduced. Holes should also be on at least two sides across from each other, and depending on size and placement may need to be on all sides of the tub. This way, there is airflow between the holes preventing stagnant air from building up. Some isopods are more tolerant of poor airflow conditions but for others the population will wane and slowly die off, even when all other conditions are perfect.
For most species, a cheap and simple method to provide ventilation is with a soldering iron typically used as a wood burning tool. Soldering irons heat up, melt through, and burn plastic. Burning plastic can emit harmful chemicals, so it is good practice to wear a protective work mask in a well-ventilated area while doing this. The holes from a soldering iron are only about 2-3mm in diameter, so in order to achieve adequate ventilation with this method we recommend putting holes around the entire circumference of the tub; each hole should be no more than 5mm apart. Soldering irons can also be used to cut out sections of plastic, but this is a very time consuming process and I sincerely do not recommend it.
The small holes of a soldering iron may not be enough for some species, and the large single hole produced increases the risk of babies lost. To combat these issues, vents can be used as a source of airflow. Circular vents are available on the market in screen, metal, and plastic options. Vents range in sizes of 1”, 2”, 3” or even 5” and up. We personally recommend using a 3” vent. Many people avoid buying the actual vents because this can be expensive, but vents can be fashioned out of fabric or window screening as well.
The process of installing vents is intimidating at first, but relatively simple once the process is understood. Hardware stores sell circular drills of an accompanying size for the diameter of a vent, and employees are happy to help find the needed size. The amount of holes depends on the size of the tubs and vents. For our 25L tubs, we do 4 3” vents, so 10-15% of the sides of the tubs are vents. When drilling holes, initially drill clockwise (the correct way) to gain traction for the drill, then the remaining portion of the hole, drill counterclockwise (backwards). This way the hole is mostly created by heat and not friction, greatly reducing the incidence of tubs cracking. Once the holes are made, the vents can be popped right in!
If you prefer to not use vents, other materials can be used to cover the hole. Be careful with your selection, however – isopods can chew through many fabrics. The two materials we recommend using are window/screen mesh and weed matting. Screen mesh has a range of thicknesses, and the more dense it is, the fewer bugs can get through it. If the spacing between the mesh is larger than 1mm, baby isopods are at risk of falling through it. To be sure the isopods don’t escape, use mesh that is rated for insect prevention use. Weed matting is a tough material used for garden beds to prevent weeds from rooting in rock gardens, making it an excellent durable material to use. Since weed matting is so tightly woven, this is a great option for micro isopods like dwarf white. The mesh covering can be attached across the hole openings with a hot glue gun, “professional” glue guns make the task a lot easier due to a much larger size and are available for as low as $15. If using screen mesh, the setup may have to be misted more frequently as this type of ventilation will dry out more quickly than weed matting or the clip in vents.
Some space should be left empty in the tub in order for air to circulate. This “dead space” should be a completely empty space with no leaves or hides. If a tub is packed full of leaves to the brim, the air will become stagnant no matter how much venting is installed. This is also particularly important for cave species such as Porcellio bolivari, many Thai Cubaris species, and species hailing from cliffs like Porcellio expansus. These animals are accustomed to a large amount of air flow naturally, and need the additional space to move around.
Ventilation with isopods can be a difficult concept to grasp. When in doubt, always strive for too much ventilation rather than too little. CO2 poisoning is an insidious threat that creeps up and claims the little lives of isopods suddenly, while too much ventilation can easily be managed with frequent misting or blocking off the excess holes.