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Changing Isopod Substrate

A big part of keeping any animal healthy is keeping them clean. Isopods, like all animals, have waste from eating. This waste is called “frass”, or bug poop. The waste of all invertebrates is called frass, roaches, beetles and other insects included.

Itty bitty square poops. Their buttholes don't look square so I'm not entirely sure how this happens, honestly.

The frass of isopods is usually small, brown, and square. It can be a bit difficult to differentiate frass from substrate. Larger species with excrete larger frass. Frass gathers on the top layer of the setup on top of the substrate; it is lighter so it rises to the top and because isopods poop on top.

A little bit of frass isn’t a big deal, but frass continues to build up over time and causes problems. Frass doesn’t retain water well, and a thick layer prevents water from reaching the substrate, so the setup dries out faster. Frass, being waste, doesn’t have the nutritional content that substrate does, and the population may plateau or even begin to reduce if they don’t have access to substrate. Baby isopods do benefit from eating a small amount of frass, it assists in establishing gut bacteria, but they don’t need a tub full of it to be able to do this.

Behold, the beautiful sand scooper.

So when should the substrate be changed? It’s as tricky as it sounds. Isopods are very small and numerous, and it is a bit of a challenge removing the frass and not the isopods. The easiest way to remove frass (and keep most of the isopods) is to use a sand sifter. Sand sifters are sold in the reptile section, and are typically marketed for sifting through sand to remove bearded dragon waste. The size and shape of frass is roughly the same as sand, so this makes it ideal. Our method is to remove the leaf litter and hides and place into a separate container. Then, sift the frass into a bucket, and put what is leftover into a separate bucket. Continue with this method until the top layer of the setup is frass free, then gently spread the contents of the second bucket back in the setup (this will be full of isopods). Spread out the leaf litter on top and the setup is just like new! Sometimes there is so much frass, the substrate needs to be replenished, but this should be added before adding the isopods. It varies by species, but some isopods will not be able to burrow out and may suffocate.

Look at alllllll those poops

Isopods, if offered a good substrate, will eat and consume the substrate with the rest of food offered in their setup. Over time, the entirety of the substrate may be converted to frass. In cases like these, the top layer of the setup is where nearly all of the animals will be, so it is not necessary to sift the entire setup, just the first layer. We recommend sifting the first layer, gutting the remaining part of the tub, and replenishing the setup with fresh substrate.

All this clumpy gunk is no bueno for moisture.

After many times of sifting substrate, thick clumps of dirt, rocks, charcoal, and perlite gather in the setup. This is a problem because these items also discourage water retention, and have no nutritional value. When the soil is very gritty like this, it makes it difficult for the isopods to molt correctly and many will die due to failed molts. It also causes an uneven distribution of water, and encourages water to gather at one end of the setup, which also may cause deaths from it being too wet. This can be amended, but it’s a bit of a painful process. The isopods need to be manually removed. To get the bulk of the animals, we recommend saturating the setup with water and offering an egg flat on top for the isopods to crawl onto. The egg flat will absorb water, but the isopods don’t like to be soggy and will crawl onto it. Wait about 10-20minutes, then gently hit the top of the crate over a container to remove the isopods. Continue this process until there are few to no isopods crawling onto the crate. There will be some isopods remaining in the setup; these will have to be plucked out by hand.

Baby isopods are hide n seek champs, and their parents' frass is their favorite spot!

A big concern for many keepers is how to save the baby isopods that may fall out when sifting the frass. There are two ways that baby isopods can be rescued from frass, but they are both terribly time consuming and we don’t really recommend it. The first method is to place the frass in an additional tub and removed the babies as they grow, and collect on an egg crate. Since the frass doesn’t retain water well, it will have to be mixed in with substrate if the babies are to survive and grow. At this point it’s really like having an entirely new tub of isopods, if we’re being honest. The other method is to manually remove each and every baby from the substrate. Now, we HAVE done this but save it for the very expensive species as it is an extremely time consuming. For the greatest success, have a very bright light on the work station. It’s also really good practice to additionally have a headlamp on to make the work area even brighter. Now, it’s really not terribly efficient to sort through the substrate while it is still in the setup. Remove small amounts of the substrate and spread out thinly in a large container. Use a spoon and a paintbrush, and gently brush any isopods into the spoon and put in the new container. This may take hours, depending on how large the setup is. When removing the babies, keep in mind that they dry out very quickly in comparison to the adults, so place them either in the new setup with the adults right away, or in a container with moist substrate.

How often should substrate be changed? This is a process that is very dependent on the size of the culture and what species the culture is. Isopods that reproduce more quickly, like P. scaber, produce more frass. Slowly reproducing isopods, like Cubaris don’t make much frass. A small starting culture of isopods (10-50ct) likely won’t need a substrate change for 6 months to a year. For small cultures, every baby is precious, so it’s best to not sift out the frass and instead upgrade the setup to a larger container. Our cultures have thousands of isopods in them, so we have to change the substrate every 3-4 months to keep everyone healthy.

Bucket O' Frass

Now that the frass is all removed, it’s time to dispose of it. According to USDA recommendations, used substrate should be microwaved or frozen to avoid introducing contaminants into the local environment. “Contaminants” doesn’t just include isopods, which is why using something like a CO2 bomb isn’t sufficient. A big concern is bacteria or viruses that captive isopods may harbor, and microwaving or freezing them will prevent introducing most harmful microorganisms. Once the substrate has been sufficiently processed, it can be spread over a garden or dumped into a trash bin.

Substrate changes are a stressful but necessary aspect of isopod keeping. Pace yourself when doing this because it’s easy to get burned out with this repetitive task. Also, we find it’s best to stand or at least work on tubs on an elevated surface for the sake of your back. Please observe USDA protocol to keep the local environment healthy, and most of all enjoy these beautiful little animals!

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Sara Klips
Sara Klips
Oct 09, 2021

You can likely remove isopods from frass (even babies) with a modified Burlese funnel with the alcohol replaced with fresh moist bedding.

Emiliano Portillo
Emiliano Portillo
Dec 18, 2022
Replying to

That is such a good idea!

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