Complete Guide to Algae Control in Aquariums | Causes, Removal, and Prevention Methods by Type

Algae that attaches to the glass surfaces and aquatic plants in an aquarium is one of the most troubling issues for tropical fish keepers. Since the causes of algae occurrence vary by type, the countermeasures also differ. Simply cleaning indiscriminately will not solve the problem fundamentally, so it is important to understand the true nature of algae and implement countermeasures tailored to the cause. In this article, we explain the causes and countermeasures for the most common types of algae. If you have just set up your aquarium and want to review the basic management steps from the beginning, please also check the Complete Guide to Setting Up a Tropical Fish Aquarium.

Causes and Countermeasures for Brown Algae (Diatoms)

Brown algae is the most common brownish algae that occurs in the early stages of setting up an aquarium, spreading in thin films on glass surfaces and substrate. The main causes are the presence of silicates and nitrates in the water, and it tends to occur when the filter in a new aquarium is not yet functioning sufficiently. Brown algae itself is not harmful to fish, and since it often decreases naturally as the aquarium matures and bacterial balance stabilizes, there is no need to worry excessively. As a countermeasure, introducing algae-eating organisms such as otocinclus or nerite snails is effective. A group of 3-5 otocinclus can remove brown algae from a 60cm aquarium within 1-2 weeks. Brown algae on glass surfaces can be easily removed with melamine sponges or magnetic cleaners. Adjusting the lighting time to 6-8 hours is also effective.

Types and Countermeasures for Green Algae

Green algae comes in the most varieties, including spot-type green algae (green spot algae), filamentous green algae (string algae), and film-type green algae that spreads thinly on glass surfaces. Green spot algae consists of hard green spots adhering to glass surfaces, with the main causes being excessively strong lighting or overly long lighting periods. It is physically removed with a scraper, and lighting time is shortened. String algae is algae that extends from aquatic plants or driftwood in thin, thread-like strands, caused by an imbalance in nitrogen and phosphorus levels in the water. Amano shrimp and Siamese flying fox eat string algae very well. Increase water change frequency to expel phosphate, and reconsider fertilizer application amounts. Blanket weed is green haze floating on the water surface, and should be removed by hand before performing a water change.

Causes and Removal Methods for Black Beard Algae

Black beard algae is troublesome algae that troubles many aquarists. It grows in short, hair-like strands of black to dark purple color on filter outlets, the edges of aquatic plant leaves, driftwood surfaces, and more. The main causes are the accumulation of phosphate and uneven water flow. For aquatic plants with black beard algae, trimming the leaves is most effective, and for driftwood, removing it and painting undiluted wood vinegar with a brush, leaving it for 5 minutes, then rinsing with water will kill it and turn it white. Whitened black beard algae will be eaten by shrimp and fish. As fundamental countermeasures, it is important to regularly clean the filter to prevent phosphate accumulation, maintain appropriate feeding amounts, and reduce areas where water flow directly hits. Adding phosphate-absorbing media to the filter is also effective.

How to Handle Cyanobacteria

Cyanobacteria is not strictly algae but rather a type of photosynthetic bacteria, characterized by a distinctive unpleasant odor. It covers substrate and glass surfaces in slimy blue-green to dark green film-like layers. The causes of occurrence are stagnant water flow, excessive accumulation of organic matter, and insufficient filter maintenance. Since algae-eating organisms do not eat cyanobacteria very well, the countermeasures focus on physical removal and environmental improvement. First, physically remove cyanobacteria that can be sucked up with a pipette or tube. Then, adjust the position of the water flow pump to eliminate stagnant areas, and thoroughly clean the substrate. Complete darkness (turning off lighting for 3-5 days and covering the aquarium) is also effective, but since it also damages aquatic plants, consider it as a last resort. Erythromycin-based antibiotics are effective against stubborn cyanobacteria, but since they also affect beneficial bacteria, use them with caution.

Daily Aquarium Management to Prevent Algae

Daily aquarium management to prevent algae occurrence is essentially basic aquarium maintenance itself. Set lighting time to 6-8 hours per day and manage it with a timer. Avoid placing the aquarium in direct sunlight. Feed amounts should be only what can be eaten within 2-3 minutes, eliminating leftover food. Excessive feeding is the biggest cause of increased nitrogen and phosphorus, which are nutritional sources for algae. Perform water changes once a week, targeting about 1/3 of the total volume. Clean the filter about once a month by gently rinsing it with aquarium water. By planting aquatic plants abundantly, you can create "biological competition" where the water's nutrients are contested between algae and plants, thereby suppressing algae growth. If you want to create a beautiful layout while also suppressing algae, the aquatic plant combinations discussed in Basics of Aquascaping are also helpful references. Algae-eating organisms are also effective for prevention, with otocinclus, Amano shrimp, and nerite snails being standard as the "three sacred treasures of algae prevention."

Biological Weapons for Algae Control

For algae control in aquariums, introducing organisms that eat algae (tank mates) is effective.

Since it is difficult to completely remove algae using biological weapons alone, it is important to combine them with lighting time management (6-8 hours per day), appropriate fertilizer amounts, and regular water changes.

You Can Also Consult About Algae-Eating Organisms at BreederDirect

It is efficient to leverage the power of organisms for algae control. At BreederDirect, if you tell breeders about your aquarium situation, they can propose the optimal algae-eating organisms. You can obtain healthy individuals of shrimp and otocinclus that breeders have carefully raised, and you can also receive advice on management after introduction.