So You're Thinking About Going Bioactive
What is Bioactive?
People use the term 'bioactive' to describe a substrate that is more natural and essentially self-cleaning. Within the context of rats, only semi-bioactive set-ups can be created, though throughout I'll be referring to it as 'bioactive' for simplicity. This is because the plants required for a complete nitrogen cycle wouldn't last a day in a rat set-up and the soil couldn't cope with all of the urine and faeces that a group of rats would create. Litter trays are therefore required to reduce the pressure on the soil.
To achieve a semi-bioactive set-up, 'Clean Up Crew' (CUC) are required. CUC are small invertebrates such as springtails or isopods that clean the soil so that mould doesn't grow.
Why Bioactive?
As someone who has kept their rats on bioactive soil for the past 3+ years, I will be inherently biased. But using bioactive soil as a substrate has many benefits. It offers brilliant and extensive digging and tunnelling opportunities for your rats. While it is expensive to set up, it costs less than conventional substrates over time. It also reduces waste and time taken to clean out. I've also found that rats with chronic respiratory issues can do very well on it as it holds a higher humidity than traditional substrate choices. I find that soil smells nicer and is more attractive. Soil is also easier to hoover up when it's inevitably kicked out.
What do I need to do?
1. Measuring for the Perspex Base
You will need to make a perspex (or other suitable material) base for your cage to hold the soil. Measure the length and width of the base INSIDE your cage. Measure for the desired height of your base; I recommend a base that is ~400mm high to allow for tunnelling and prevent large amounts of soil ending up outside of the cage. Make these measurements, in millimetres, carefully so that you don't make any mistakes, which can be costly to fix!
Calculate the measurements of each pane - there are 5 in total. These measurements should take into account the thickness of the perspex sheets, with a couple of mm removed to account for any errors and allow an easier fit into the cage. Below are some example measurements using my Little Zoo Venturer cage, but always do your own measurements as even the same cage may vary slightly.
I ordered my perspex made to measure from The Plastic People.
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2. Assembling the Perspex Base
Once the pieces have arrived, you can join them together using strong tape or adhesive. I used industrial-grade super glue (which was left to dry) and clear gorilla tape for mine. If you followed the measuring guide above, you want to place the 4 sides on top of the base. The photos below, kindly provided by Mary Giles (Zephyr Stud), show the adhesive and tape that can be used to fix the perspex sheets together and a shallow base in construction (used for more conventional substrate). Another photo also shows a mostly opaque base, which is another option if that is your preference.
3. Filling the Perspex Base
Fill your perspex base half-way with coco fibre soil and/or top soil. I prefer to use coco fibre soil as it has more texture, and top soil can come with small rocks (which my girls love to chuck down the side of the cage).
Dust-extracted hay is also a great option for improving the texture of the soil, allowing tunnels made to hold their shape better. You can add in sphagnum moss for moisture retention and soil texture.
Cork bark is a great addition to any bioactive substrate. It provides a safe haven for clean up crew and is great for chewing and climbing while offering additional structure to tunnels.
Add in your clean up crew - springtails should suffice. You can also add in earthworms and isopods from a herptile shop, but these may be hunted down and eaten. You cannot add animals from outside as they may carry parasites etc that you don't want in your soil and/or rats.
4. Maintenance and Care
You should water your soil when it is dry and give the surface a light turning. The soil should clump when squeezed. Your soil has been overwatered if water drains from the soil when squeezed.
If your rats don't dig a lot, turn the soil weekly. If your rats are avid diggers, you can get away with turning the soil monthly.
You should add more springtails/clean up crew if there are areas of mould. Consider keeping your own colony to cut costs. Springtail care is quite easy - keep them in a small faunarium with some soil and a small piece of cork bark, then feed them oats.
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Soil Pests
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The main downside to a bioactive setup is when the soil attracts unwanted occupants such as fungus gnats or indian meal moths. The best thing to do is to target the pest at each life stage to stop reproduction and kill off the adults. If you only target one aspect, they are more likely to persist. Below are some ideas of things to try:
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1. Sift through the soil to check for pests and store in a sealed box/bag until the infestation has been dealt with.
2. Soak cork bark/other items from the soil in hot water, dry, then store in a sealed box/bag until the infestation has been dealt with.
3. If the pest likes wetter conditions, let your soil dry out more than usual.
4. If the soil is staying in situ, keep adding more clean up crew to compete with the pest.
5. Put up traps for the adults. Sticky traps and bowls of water can be attractive.