In this article, aquarium algae types, causes, and removal methods are given with general information. Most of the curing methods in this article are immediate and temporary actions. The basis of getting rid of algae is the balance in the aquarium. You can refer to this article about the balance in the aquarium.
It is very common within the algae types that appear in most aquariums at one point or another. It also has types as Hair algae, Thread Algae, Green Spot algae, Green Dust Algae, etc. depending on its appearance and texture. It appears either as spots, coats, or threads (with hair or thread-like projections) on surfaces of decorations, equipment, substrate, and plant leaves.
The growth mainly occurs due to:
• Excess lighting
• Low CO2 levels
• Nutrient imbalance (Nitrogen-compounds, phosphates, or potassium)
• You can remove softer variants like hair or thread algae easily with a scrub or cloth. Harder green algae types like the Spot Algae or green dust algae are harder to remove and need to be scraped off with a razor.
• Alternatively, you can have algae-eaters like Nerite snails (Neritina sp.) in your aquarium as they will do the scraping for you.
• As a last resort option, use of Hydrogen Peroxide spraying over the algae or use of commercial anti-algae solutions.
• Blackout the tank for 3-5 days.
Addressing the Cause
• Reduce the brightness and lighting periods.
• Test the water. If any of the macronutrients (Nitrogen-Phosphorous-Potassium) are low, you can increase their concentration using the corresponding fertilizer. If the concentrations are high, massive and more frequent water changes (30-50% each week) will be helpful.
• To balance nutrient levels, do not overfeed the fish.
• Increase CO2 levels. Use a CO2 injection system or liquid carbon reagents (like Flourish Excel by Seachem Laboratories). However, too much CO2 can be harmful to aquarium species. Keep the concentrations at safe levels.
Brown Dust Algae (Diatoms)
Brown algae is another very common algae type that exists in aquariums, especially in newly set-up aquariums. It forms brown coats on all surfaces including glass, substrate, decorations, plants, and filter equipment.
A newly setup aquarium undergoes a natural cycle of biological growth. Brown algae start to appear in 1-3 weeks and get crowded out by other algae types, especially green algae within 1-3 months.
In a more established aquarium, a combination of the following factors contributes to its growth.
• Low-intensity lighting
• High silicate levels
• High nitrate levels
If the aquarium is newly set up, you do not need to take any counter-measures to remove brown algae. It will disappear gradually because of competition with other algae types and plants.
If it does not disappear after a while or if it appears in a more established aquarium, you need to remove the aquarium decorations or filter equipment and scrub them with a sponge or cloth. You could also dip them in a 10-20% bleach solution to completely kill off the algae. But it will help temporarily like most of the other chemical treatments.
Addressing the Cause
• Increase the aquarium lighting and replace light bulbs older than 8-12 months.
• Filter the water source with a Reverse Osmosis unit or introduce special filter media to eliminate the silicates. Also, make regular water changes to keep the nitrate level below 25 mg/liter.
• Ancistrus dolichopterus is good at eating diatoms.
Blue-Green Algae (Cyanobacteria)
Cyanobacteria, also called Blue-Green algae, are bacteria that can photosynthesize like most microflora. It has an unpleasant odor and a slimy texture, so It is also called Slime or Smear algae. It appears as thin sheets in the aquarium, covering different surfaces like gravel, stones, and plants. It usually has a blue-green look in freshwater tanks, but can also display dark green or black coloration. In marine tanks, it has a reddish coloration.
A combination of the following factors contributes to the growth;
• Low-intensity lighting.
• Phosphate (PO4) and Nitrate (NO3) level imbalance.
• Stagnant water with low aeration.
• Organic waste settlement over the substrate and plants.
• Insufficient filtration and nitrification efficiency.
• Overfeeding and overloaded organic load.
• Use of UV Sterilizers with a heavy organic loaded aquarium. UV will cause additional organic load (dead organisms) on the tank’s load capacity.
• You can remove it manually using a net or a gravel cleaner.
• Although commercially available chemicals like Erythromycin will kill this bacteria. But these kind of products are affecting also other algae types of beneficial bacteria and can disrupt the ecological balance in the aquarium.
• Do a large water change (30-50%). Follow it up with small water changes (10-20%) on alternate days for a week. Reduce the feeding levels to one-third of normal levels till the algae disappear.
• Blackout the tank for 3-7 days.
Addressing the cause
• Replace the light bulbs of the aquarium that are older than 8-12 months.
• Feed the fish only once per day.
• Add air stones or turn up the powerheads to improve aeration and flow.
• This algae mostly grows on organic debris in the first phase and then covers the tank. Thus, regular sifting of the gravel will help prevention of this algae.
Green water or Algae Bloom occurs due to the overgrowth of microscopic algae that float in the water. These algae reduce the visibility and lower the oxygen levels of water. It will also prevent light to reach the bottom of the aquarium and the plans. This will harm the plants and impact growth.
• Excessive lighting, especially direct sunlight.
• High nutrient levels due to overfeeding or overpopulation of aquarium.
• High ammonia (NH4) levels.
• Increase in temperature due to changing seasons.
• New aquarium setup.
• Excessive release of nutrients from substrates for plants.
• In less severe cases, making large water changes (20-40%) and eliminating the causes is enough to cure Green water.
• In severe cases, you may need to opt for black-out treatment. Shield your aquarium from all light sources for 5-6 days. Feed your fish only on alternate days during this period. The algae should die off within a week as they will not receive any nutrition or lighting. Follow this up with regular water changes to remove the dead organisms.
• Use a diatomic or low micron rating filter.
• UV sterilizer can also eliminate microscopic algae effectively within a week, though leaving it on for too long could harm the ecosystem and load additional organic dead matter.
• Add daphnia or Fairy shrimp into your tank. These creatures feed on the microscopic green algae and in return, get eaten by fish.
Addressing the Cause
• Do not keep your aquarium under direct sunlight. Even indirect sunlight (light bouncing off from walls) aids significantly in the growth of algae.
• Feed your fish only once a day. Any food which is not accepted by the fish within the first two minutes is excess.
• Use fertilizers at necessary levels especially nitrogen and phosphate.
• In new setups do not fertilize the tank for at least 1-2 months. Instead, do regular water changes.
Black Beard Algae (BBA)
Beard algae or Brush algae is a type of red algae that is very hard to remove. It grows on the edges of plant leaves, and other hard surfaces like filter equipment, rocks, or substrate. It can have bright green, blue-green, brown, or black coloration. It resembles a dirty beard or small bush and grows very rapidly.
• Low or fluctuating CO2 levels.
• Nitrate and phosphate level imbalance.
• Dip the affected plants, driftwood, rocks, or equipment in 10-15% bleach solution. Trim the leaves or stems of plants that are affected.
• Use liquid carbon reagents (Flourish Excel by Seachem or Easy Carbo by Easy Life) or hydrogen peroxide (H2O2) solution. BBA will first turn purple or pink, and then die off after a few days of treatment and turns white.
• Many aquarists keep Siamese Algae Eater (Crossocheilus siamensis) as it grazes on BBA very efficiently.
Addressing the Cause
While low CO2 levels and nutrient imbalance facilitate its growth (higher levels). BBA usually enters the aquarium through affected plants or driftwood. So, the best way to deal with it is to prevent it from entering the aquarium. You must buy all aquarium plants and equipment from a reputable source, and ensure that they are clean before introducing them into the aquarium.