Staghorn algae (SGA) is a common nuisance algae that plagues many planted aquarium enthusiasts, often appearing suddenly and spreading quickly. This organism is a form of red algae, scientifically known as Compsopogon, which thrives when the delicate balance of a planted tank environment is disrupted. Eliminating this persistent algae requires understanding its distinct visual characteristics, the underlying environmental instability that allows it to flourish, and a long-term strategy for ecosystem correction. Addressing its root causes is the only effective path toward a clean, thriving aquarium.
Identifying Staghorn Algae
Staghorn algae is visually distinct, making proper diagnosis the first step in effective treatment. It presents as stiff, stringy tufts that are dark green, grayish-black, or sometimes off-white. The name derives from its branching structure, which resembles the horns of a stag, with individual strands often growing several centimeters long.
This algae is frequently found attached to the edges of slow-growing plant leaves, such as Anubias and Bucephalandra. It also colonizes hardscape elements, filter intakes, and heater tubes, favoring areas with moderate water flow. SGA is generally much stiffer and longer than Black Beard Algae (BBA), making it difficult to wipe or rub off manually.
Primary Environmental Triggers
The sudden appearance of staghorn algae indicates that the aquarium’s ecosystem has become unstable, favoring algal growth over healthy plant growth.
Insufficient or inconsistent carbon dioxide (CO2) delivery is a common cause in high-tech planted tanks. When CO2 levels fluctuate or drop too low, aquatic plants become stressed, encouraging algae attachment.
Another trigger is an imbalance in the nutrient profile, particularly a buildup of dissolved organic compounds (DOCs) like ammonia and nitrites. Staghorn algae readily utilizes these simpler nitrogen compounds, gaining a competitive advantage over plants that prefer nitrate. Furthermore, an overall nutrient imbalance, such as an excess of iron or other micronutrients relative to macronutrients (Nitrogen, Phosphorus, Potassium), can also create conditions for SGA to thrive.
Poor water circulation is the third destabilizing factor. Stagnant zones prevent essential CO2 and nutrients from reaching the plant leaves, especially in dense planting areas. This localized starvation stresses the plants, creating pockets of imbalance where staghorn algae can easily take hold.
Immediate Removal and Treatment Methods
While addressing the root cause is necessary for long-term control, immediate action must be taken to stop the current outbreak.
Manual removal involves the physical trimming of heavily infected plant leaves to prevent the algae from spreading. Hardscape elements should be removed from the tank, if possible, and scrubbed clean with a stiff brush.
For targeted chemical treatment, a 3% solution of hydrogen peroxide (H2O2) is effective. The most direct method is spot treating the algae by turning off water circulation and injecting H2O2 directly onto the affected area using a syringe or pipette. A common starting dose is around 1 milliliter of 3% hydrogen peroxide per 1 gallon of tank water, ensuring a few minutes of contact time before restarting the flow.
Alternatively, liquid carbon products containing glutaraldehyde can be spot-dosed directly onto the algae. Following any chemical spot treatment, perform a large water change, ideally 50% or more, to remove oxidized organic matter and residual chemicals. This treatment will cause the staghorn algae to turn pink or white, indicating it is dead.
Achieving Long-Term Tank Stability
Preventing the recurrence of staghorn algae requires establishing a consistently stable environment that favors plant growth.
Optimizing CO2 delivery is paramount, aiming for a concentration of 20 to 30 milligrams per liter, especially in high-light, high-nutrient setups. The CO2 injection must be stable and consistent throughout the light cycle, monitored using a drop checker that maintains a steady lime-green color.
Nutrient calibration involves testing water parameters to ensure a balanced fertilizer regimen. The goal is to maintain adequate nitrogen (nitrate) levels, typically between 10 and 25 milligrams per liter, relative to other macro and micronutrients. Ensuring the plants have all necessary elements in proper proportion allows their robust growth to naturally outcompete the algae.
Enhancing water flow is also necessary to eliminate dead spots where nutrients and CO2 accumulate or deplete. Adjusting filter outputs or adding a small powerhead ensures water turnover effectively reaches all areas, preventing localized plant stress.
A consistent maintenance routine, including weekly partial water changes and regularly cleaning detritus from the substrate and filter media, is the final element in stabilizing the ecosystem.