Bioactive Terrarium Build

rattlesnake plant in terrarium

rattlesnake plant in terrariumBack in my younger days, I would always wear the coolest t-shirt from Rainforest Café. It came with a bunch of clasp-on rainforest bugs that I could use to prank people, show off, or entertain myself when I was bored. Now, I’m managing my own miniature rainforest within the confines of my bedroom. What I’m referring to is the bioactive terrarium setup that has become popularized in the pet community as of late. Here’s why I find this hobby fascinating.



Materials Used:

  • Medium and large sized pebbles for at least 2″ of drainage
  • At least 4″ of moisture-holding substrate such as coconut fiber
  • Leaf litter to trap moisture and feed microfauna
  • Microfauna like springtails or isopods to manage fungus and waste
  • Plants to retain moisture and enrich soil

This bioactive setup is larger than your typical terrarium-in-a-jar. My 20-gallon tall tank with a screen top allows me to water my plants or add in new pieces if needed. It’s not completely self-sustaining, but the tank maintains humidity well on its own and the springtails are content without interference. A water dish will maintain moisture in your tank as well. Just be wary that some bugs are attracted to still water.

What Grows in There?

A fittonia, pothos, and rattlesnake plant are in the tank at the moment. Leaf litter on the surface breaks down and helps feed springtails that are living in the soil. I made sure to wash and dry the leaves before adding them so I didn’t have too many unwanted insects. Egg nests hidden in leaf litter can release critters that will be difficult to get rid of later. Small leaves are preferable- I tried adding larger ones and they didn’t fit in the tank as well. The large leaves also started to have mold spots and give off a terrible smell after a day. The smell of damp earth is bad enough. You won’t want the smell of mold on top of that.

green leaf plant
Photo by Faraz Ahmad on

I spotted my springtails hiding out in air pockets at the bottom of the soil layer where moisture is highest. Although many died in transit, the population made a crazy return since then and it’s actually kinda gross. I also ~accidentally~ grew mold in my tank, which quickly died off once I increased direct light and temperature. I spotted a single gnat once which was probably attracted to the high moisture, leaf litter, and mushrooms that I used to feed the springtails. Thankfully I haven’t seem him in a while. Sometimes experiments like this can go sideways and you can end up growing something you weren’t trying to.


An extension cord with a timer helps turn the tank light on during the day. Aluminum foil aids in keeping up humidity. One day the tank got up to 100% humidity, which was impressive for being in a room that was around 69 degrees and very dry. The thermometer and hygrometer readings can change depending on where in the tank they are. I found that part particularly interesting because there truly are micro-environments at play here.

green caterpillar on green plant stem
Photo by Pixabay on

Animals can experience vastly different environments in the same general space. Things like temperature, humidity, direct sunlight, and wind are completely different for me than they would be for a caterpillar for example. A caterpillar is going to feel moisture from evapotranspiration on a leaf’s surface whereas a human such as myself would have to be blown over before I noticed it was even windy outside. Scale changes things incredibly. In terms of my tank, if the topsoil dries out, I can rest knowing that the springtails are hiding just a few millimeters below the surface in a space that is insulated and humid enough for their liking. They are living in a humid micro-environment.



Burlap was used as a background for the tank and was affixed with magnets for easy removal. The thermostat shown above monitors temperature at the sensor location and turns off the side tank heater when an ideal temperature is reached. The temperature inside stays around 75 when using just the side tank heater because of its small size. I think some heat is being reflected backwards so adding a panel behind the heater could help limit that. I’m not attaching a picture of the springtails for good reason. Trust me.

Future Work and Worries

A friend of mine who happens to be an animal aficionado gave me a solid yet simple piece of advice in this bioactive business. I was worried what would happen if my terrarium got gnats? Or grew fungus? Got overrun with mold? Started sprouting mushrooms?

close up photo of mushrooms
Photo by Chris Gonzalez on

He responded that those things all happen in nature. So what if I had gnats? And why be afraid of mushrooms? People will tell you not to add moss or leaves from outside to your terrarium because it could have bugs or diseases. While that’s true, there is also no reason to fear a perfectly functioning ecosystem. Pests exist in the real world, but everything balances out. Plastic decor has its own issues. In the end, trying to replicate the natural environment is a bit toilsome. Mistakes help you improve and learn from the experience.

The great thing about sizable terrarium setups is that they are friendly for terrestrial frogs and other fascinating companions. I’ll be posting again soon with updates on what’s living in my terrarium. I hope to add more plants that can handle high heat and moisture.

Did you ever try making the world in a jar? What about in a tank? Add your thoughts in the comments below. Sincerely, Jess

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