White fungus on driftwood – what is it?

White fungus on driftwood is a common phenomenon observed in aquariums, particularly in tanks with newly added decorative wood. This substance, often appearing as a white, cotton-like or slimy coating, develops on the surface of driftwood due to the growth of natural fungi and bacteria that decompose organic material. When driftwood is submerged in water, it begins to release natural compounds, including tannins and sugars, which serve as food for microscopic organisms. As a result, the white layer becomes visible. Although it may look alarming to aquarists, this occurrence is not usually harmful to fish or plants. In fact, it can be part of the natural cycle of an aquatic ecosystem, often disappearing on its own after a few weeks. The presence of white fungus on driftwood is frequently observed in the first 2–6 weeks after introducing the wood into the aquarium. During this period, fish such as plecos, shrimp, and snails often feed on it, helping the aquarium reach balance. Some aquarists even consider it an indicator that the aquarium is developing a stable biological environment. However, understanding why it appears, how long it lasts, and how to manage it remains important for maintaining both the visual appeal and health of the aquarium.

Why does white fungus on driftwood appear?

The appearance of white fungus on driftwood can be explained by a combination of biological, chemical, and environmental factors. When driftwood is submerged, it undergoes hydration and begins to release soluble organic compounds. These compounds, such as cellulose, lignin, and tannins, provide an abundant food source for naturally occurring aquatic microorganisms. Fungal spores and bacteria, which are almost always present in aquarium water, take advantage of these compounds and multiply rapidly, creating the visible fungal colonies. The growth is not dangerous; in fact, it indicates that organic material is breaking down naturally. The structure of the wood also plays an important role. Softer wood types, such as mopani or certain roots, tend to leach more organic matter than harder woods, thus showing thicker fungal growth. The white layer is actually a biofilm, a mix of fungi, bacteria, and other microorganisms living in a slimy protective layer. In nature, similar biofilms develop on submerged wood in rivers and lakes, and aquatic animals graze on them. Aquariums are no different. The quantity and duration of white fungus on driftwood can depend on several variables:

• Age of the driftwood – freshly collected or recently purchased wood releases more organic compounds than aged, pre-soaked pieces.
• Water temperature – higher temperatures often accelerate microbial growth, sometimes making the fungus appear thicker.
• Aquarium circulation – tanks with weak water flow provide ideal conditions for biofilm accumulation.
• Type of inhabitants – aquariums stocked with fish and invertebrates that graze on biofilm often show reduced fungal patches.

For many aquarists, the sudden appearance of this white substance can feel alarming, especially because it may resemble mold or disease. However, careful observation reveals that it rarely harms aquarium life. The growth is temporary, and after 3–6 weeks, most driftwood stops releasing enough nutrients to sustain the fungus, leading to its gradual disappearance. Even in cases where it persists longer, regular cleaning and biological control using algae eaters, shrimps, or snails help to keep the driftwood surface clean. Therefore, the phenomenon should be seen not as a threat, but as a natural process reflecting the balance of life within the aquarium.

How to manage and prevent white fungus on driftwood

Managing white fungus on driftwood requires a combination of observation, maintenance, and patience. Since this growth is not inherently harmful, the best approach is often to allow nature to regulate itself. Many aquarists observe that within 20–40 days, the white film disappears without intervention. Still, when the appearance of the fungus becomes excessive or affects the aesthetics of the aquarium, practical steps can be taken. The first method involves manual removal. Using a soft brush or siphon tube, aquarists can gently scrub or vacuum off the fungal layer during routine water changes. This reduces its visibility but may not completely eliminate it, as spores remain in the water. The second method is biological control. Introducing shrimp, such as Amano shrimp or cherry shrimp, and certain species of snails, including nerite or mystery snails, proves highly effective. These animals feed eagerly on the white biofilm, often clearing the driftwood surface within days. Additionally, some bottom-feeding fish, such as Plecostomus or otocinclus, contribute to managing the fungus. Another strategy involves pre-treatment of driftwood before placing it in the aquarium. Boiling the wood for 1–2 hours or soaking it for several weeks in a separate container allows much of the excess organic matter to leach out before introduction. This significantly reduces the likelihood of fungal growth. Regular water changes are also essential. By replacing 20–30% of the aquarium water weekly, aquarists limit the nutrients available for fungal colonies. Good filtration, combined with adequate circulation, prevents stagnation and lowers the intensity of fungus formation. Some aquarists even use activated carbon in their filters to absorb excess organic compounds released from the driftwood. It is worth noting that chemical treatments should generally be avoided. While some antifungal aquarium products exist, they are unnecessary and may harm sensitive organisms. The natural balance of the aquarium proves to be the most reliable remedy. In the long term, once the driftwood has aged inside the tank, the growth of white fungus on driftwood becomes less frequent and often disappears completely. As an interesting observation, aquarists who own multiple tanks often notice that driftwood used in older, established aquariums rarely develops fungal growth again. This is because the majority of the soluble organic matter has already been released, and the aquarium’s micro-ecosystem has stabilized. Thus, prevention lies in proper preparation, patient observation, and maintaining a healthy aquatic environment. Managing white fungus on driftwood ultimately helps aquarists gain confidence in dealing with natural cycles and fosters a deeper understanding of how aquariums function as miniature ecosystems.