Anubias is a popular and resilient aquatic plant, valued for its tough, dark green leaves and ability to thrive in a wide range of water conditions. Many hobbyists wonder if this slow-growing plant needs dedicated fertilization. While Anubias is adaptable, providing specific nutrients helps ensure vibrant growth and prevents common problems. Whether fertilization is necessary depends largely on the plant’s unique growth habit and the existing nutrient content of the aquarium water.
The Epiphytic Nature of Anubias and Nutrient Absorption
Anubias plants are classified as epiphytes, meaning they naturally grow attached to surfaces like driftwood or rocks, rather than rooting in the substrate. This growth habit dictates how the plant acquires nutrients. The plant’s thick, horizontal stem, known as a rhizome, sprouts leaves and fine roots that primarily anchor the plant to the hardscape.
The roots and leaves are adapted to draw nutrients directly from the surrounding water column. Unlike heavy root feeders, Anubias relies on dissolved minerals and organic compounds suspended in the tank water. It can often subsist on naturally occurring nitrates and phosphates produced by fish waste. However, in low-fish-load tanks or those with aggressive filtration, these ambient nutrients can be quickly depleted, necessitating supplementation.
Recognizing Signs of Nutrient Deficiencies
Observing the leaves is the most direct way to determine if your Anubias requires more nutrients, as different deficiencies produce distinct visual symptoms. Deficiencies in mobile nutrients, which the plant can relocate from old growth to new growth, typically appear first on older leaves. For example, a Nitrogen deficiency often results in older foliage turning yellow or translucent, starting at the leaf tips.
Potassium deficiency, which Anubias is susceptible to, often manifests as small pinholes or necrotic spots along the edges and tips of older leaves. Conversely, a deficiency in immobile nutrients will appear first on new growth. An Iron deficiency causes new leaves to emerge pale green, yellow, or white, while the veins remain dark green. If you notice yellow to white patches forming a web-like pattern across the leaf surface, the plant may be lacking Manganese.
Water Column Supplementation: Dosing and Frequency
Because Anubias is a water column feeder, liquid fertilizers are the primary and most effective method for providing nutrients. These liquid supplements ensure that essential macro-nutrients (Nitrogen, Phosphorus, and Potassium) and micro-nutrients (Iron and Manganese) are immediately available for uptake. Many hobbyists opt for an “all-in-one” liquid fertilizer containing a balanced mixture of these elements.
For slow-growing plants like Anubias, a “lean dosing” approach is more suitable than high-concentration methods, as excessive nutrients can fuel algae growth. A good starting point is to dose the fertilizer at half the manufacturer’s recommended amount for the first few weeks. Dosing frequency depends on the fertilizer type and the tank’s water change schedule. A common practice is to apply a comprehensive dose once or twice a week after a water change, or to split the weekly dose into smaller, daily micro-doses.
Substrate Feeding: When Root Tabs Are Necessary
While Anubias primarily absorbs nutrients from the water, its roots can draw nutrients from the substrate if they grow into it. Solid fertilizers, commonly called root tabs, are a supplemental feeding option for Anubias whose roots have established themselves in the substrate. Root tabs are capsules packed with concentrated nutrients that release slowly into the immediate area.
This method is only necessary if the water column is consistently low in nutrients or if you are aiming for faster growth. When using root tabs, place them into the substrate directly underneath or near the established roots, several inches away from the plant’s core. Remember the main rule of Anubias care: never bury the rhizome, as this will prevent gas exchange and cause the central stem to rot.