Isopods in Terrariums: An Introductory Guide

A powder orange isopod traversing a (relatively) enormous gap.

Wanting more to look at in a terrarium? Look no further at isopods! Isopods are a great, beneficial addition to terrariums that come in a variety of colours and shapes. Depending on where you live, Isopods can sometimes be a hobby on its own where you can trade different species among other hobbyists and obtain rare varieties (with some of the most sought after varieties costing $100-$200 for 5 individuals!).
Incredibly easy to take care of in the right environment, Isopods munch on decaying material and fallen leaves in a terrarium and require no special treatment for reproduction. Isopods are most active at night but will venture out occasionally to forage.
If you are thinking of adding isopods to your terrariums, here are some things to consider:

Terrarium Requirements:

Isopods work well in terrariums where there is lots of moisture and humidity due to them not being an insect, but a crustacean with gills. Because of this, we need to make sure that they do have a good amount of moisture at all times or you may be putting your isopods at risk of dehydration.

When making a terrarium, you’ll have to understand what sort of environment works for isopods. Isopods love to dig under the surface and stay around moisture, this makes a nice soft soil like coco-peat a good choice for a substrate. When in a terrarium, it has to be expected that an isopod will displace ground cover and shift around light decorations which may make it a good idea to give any sand art or top cover extra depth.
You would at first assume this crustacean can handle sitting bodies of water like their ancestors. An isopod will drown itself in bodies of water as they still have not fully realized their transition to land life, this makes vivariums a dangerous location to keep isopods.
Finally a terrarium needs to either have enough plants to provide oxygen, ample space to hold oxygen or a lid that can be periodically taken off so the isopods do not die from suffocation. Oxygen deprivation can happen faster in high mould environments, which will sap the oxygen and convert it to carbon dioxide. All these factors will be a lot easier to navigate after the terrarium has been established and no volatile materials are inside the sealed container. If your terrarium is new and there is lots of initial breaking down in your terrarium, the carbon dioxide levels may be too high and your isopods are at risk of suffocation.

Light is not a requirement inside a terrarium but is required for any rooted plants or moss that need it to live. If bright light is present, the isopods will generally wait until the light turns off to come out from hiding.

Pieces of wood work great with isopods in terrariums, however, I always suggest the wood is boiled and submerged to ensure there are no other organisms transported into the terrarium to emerge at a later date. Some pieces of wood may also mould heavily and may need assistance to keep clean from springtails.

Sow bug or Pill bug?:

Although these isopods look like they have similar colourings, there are distinct differences of the two.

Pillbug

Sowbug

• The Pillbug is the version of Isopod that can roll up into a ball, pillbugs are generally slower than sowbugs.

• The Sowbug is overall flatter than pillbugs and are faster at moving and reproducing. Also notice the tail at the end of the sow bug, this can be an easy way of identifying between male and female isopods. From experience, sowbugs are more likely to show aggression towards other isopods.

Isopod Reproduction & Aging:

Isopods reproduce easily and in good numbers. However, the isopods life cycle takes much longer than their terrarium counterpart the springtail. When an isopod mates, the male isopod will jump and latch onto the top of the female, injecting the female with sperm. This may look aggressive at first and you might mistake this for cannibalism but this is normal.

You can identify a pregnant isopod by finding a filled pouch on the underside of the female isopod. Babies will hatch from this filled pouch after 40-50 days.
Babies generally have around 8-12 weeks to become sexually mature after birth. Baby isopods are very fragile and disruption of their surroundings can easily lead to them being crushed as they tend to hide under large pieces of food and stay burrowed beneath the surface. Baby isopods are also at risk of being eaten by other hungry and/or aggressive isopods, it helps for them to have locations where they can stay safe (e.g loose soil to burrow into).

Isopod Food:

Before going any further with this topic, in most terrariums there is no need for food to be given to isopods. Feeding isopods may increase reproduction and improve overall health but isopods will do perfectly fine just off dead plant matter. As isopods hide under the substrate for long periods, you may want to lure your isopods out just to look at them!

Isopods will eat most things available and are not too picky with what they get to eat, this makes everyday fruit and vegetable scraps a good option. Avoid placing food that will decompose on top of natural materials like moss as these plants can discolor or be damaged by moulds presence. Placing food on top of large rocks would be the most suitable place for supplementary food as you can easily monitor the food and watch it deplete, ensuring there is no mould in your terrarium at a later date.
Keep the food at a minimum to avoid mould and introduce springtails as a security measure as springtails are much more suited to eat mould if the food has broken down too much.

When food supply is low, isopods sometimes will consume terrarium plants. This may require you to test out the plants you place in your terrarium and replace accordingly. For example, In my most recent enclosure, the isopods were caught eating fittonia plants while syngoniums have always stayed untouched.

Isopods will vary their preferences for food depending on their species, due to the vast amount of species you will have to test the food preference of any type you receive.

I was amazed at how much i enjoy watching isopods go about their business. Watching them eat, run around and interact with each other is one of the highlights when I’m in the office. I would highly recommend looking into these crustaceans and working them into your hobby if you’re already interested in terrariums & beneficial bugs.