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Identifying Unknown Organisms in Your Terrarium: A Curious Discovery
Identifying Unknown Organisms in Your Terrarium: A Curious Discovery

Identifying Unknown Organisms in Your Terrarium: A Curious Discovery

Every so often, terrarium owners may spot an unexpected guest, a tiny, unidentified creature or growth that wasn’t there before. These curious discoveries may raise questions, excitement, and sometimes a little concern. 

This article will guide you on how to identify these unknown organisms and what steps to take upon discovering them in your terrarium.

Common Unknown Organisms in Terrariums

Terrariums, like any ecosystem, can host a myriad of organisms, some more conspicuous than others.

Here’s a more detailed look at some of these potential unexpected residents:

Mold and Fungi

mushrooms growing in a terrarium

Molds are a type of fungus that grow in the form of multicellular filaments known as hyphae. They often appear as fuzzy or slimy patches of various colors. While some molds are unsightly or potentially harmful to your plants, many play an essential role in breaking down dead organic material and recycling nutrients.


algae terrarium

Algae are a diverse group of photosynthetic organisms that can add a green tint to your terrarium’s glass or even form green or brown patches on the substrate or decorations. While they can be a sign of excessive light or moisture, some algae contribute to the ecosystem by producing oxygen and providing food for some microorganisms.

Insects and Arthropods

many springtails

Small insects and arthropods like mites or springtails can often be found in terrariums. While some, like aphids or certain types of mites, can be harmful to your plants, others, like springtails, are beneficial, helping to break down organic matter and control harmful pests.



This group includes various microscopic organisms such as protozoa, nematodes, and tiny crustaceans like copepods or ostracods. While usually out of sight, they play crucial roles in the ecosystem, including decomposition, nutrient cycling, and forming part of the food chain.


visible bacteria

Although not visible to the naked eye, bacteria are almost certainly present and are vital contributors to your terrarium’s ecosystem. They participate in various processes, including decomposition, nutrient cycling, and nitrogen fixation.

These organisms can hitch a ride into your terrarium through a variety of sources such as the air, water, substrate, plants, or decorative items. 

They can remain dormant until the conditions within the terrarium become favorable for their growth. 

Understanding these organisms and their roles can help you maintain a balanced, healthy terrarium.

The Benefits of Biodiversity

The sudden appearance of unknown organisms in your terrarium might initially prompt a reaction of surprise, perhaps even concern. 

However, it’s essential to remember that not all unexpected discoveries are detrimental. Many are, in fact, a boon to your mini ecosystem, actively enhancing its health, resilience, and complexity.

Decomposition and Nutrient Cycling

decaying leafs

Fungi, including various molds, are potent decomposers, integral to the nutrient cycling process. They break down organic matter – like fallen leaves or dead plant material – into simpler compounds. 

This organic breakdown is vital because it releases nutrients back into the soil, making them available for plant uptake.

Natural Pest Control

plant pests that destroy terrarium plants

Small arthropods, such as certain mites and springtails, can serve as efficient bio-controllers, keeping potential pest populations in check. They do so by preying on these pests or outcompeting them for resources. 

In this way, these tiny custodians help protect your plants from damage and disease.

Soil Health and Fertility

tropical terrarium soil substrate

Bacteria and algae, too, play critical roles in maintaining soil health and fertility. Certain bacteria help with processes like nitrogen fixation – converting atmospheric nitrogen into a form that plants can utilize. Algae, being photosynthetic, produce oxygen and can also add to the nutrient content of the soil.

Improved Resilience and Balance

The presence of a diversity of organisms leads to a more robust and balanced ecosystem. It enhances the system’s resilience, enabling it to withstand and recover from disturbances better. 

Each organism, in playing its unique role, contributes to the dynamic balance of the terrarium, helping to keep it healthy and thriving.

Recognizing the invaluable contributions of these often-overlooked organisms, it’s clear that we shouldn’t be too hasty to ‘sanitize’ our terrariums. Instead, fostering and maintaining this spontaneously arising biodiversity can lead to a more intriguing, balanced, and resilient terrarium ecosystem – a miniature testament to the power and beauty of nature’s interconnections.

Dealing with Unwanted Organisms

springtail in terrarium

With that being said, not all uninvited guests are beneficial. 

While many unexpected guests in your terrarium contribute positively to its health and balance, some might pose challenges. 

Certain organisms, such as harmful fungi, aggressive pests, or invasive plant species, can potentially damage your plants, disrupt your terrarium’s balance, or simply be an eyesore. 

Here’s how to deal with these situations:

Identification: The first step is to identify the unwanted organism. This could be a harmful mold like Phytophthora, pests like aphids or scale insects, or an invasive plant like baby’s tears (Soleirolia soleirolii), which can take over your terrarium. Use resources like field guides, online databases, or local experts for proper identification. Knowing the organism’s nature and needs is key to developing an effective action plan.

Evaluation: Next, assess the impact of the organism on your terrarium. Is it damaging your plants? Is it proliferating at an alarming rate? Is it merely unsightly but otherwise harmless? Your answers will guide your subsequent steps.

Removal: If the unwanted organism is causing harm, consider removing it manually. For example, aphids or scale insects can often be removed with tweezers or a soft cloth. In the case of an invasive plant, you might need to carefully extract the plant and its roots to prevent regrowth.

In Conclusion…

The discovery of unknown organisms in your terrarium is part of the journey, offering opportunities for learning and adaptation. 

Being vigilant and informed in identifying these new additions is key to maintaining a healthy and thriving terrarium.