One of the greatest concerns of all aquatic plant enthusiasts is algae prevention. Once algae get a foothold in a planted aquarium it can be hard to bring it under control. We’ll take a look at the different kinds of algae that make trouble in planted tanks, what stimulates their growth and how to keep algae under control. But first let’s compare aquatic plants to algae so we can understand the similarities and differences.

Plants vs. Algae

It is important to understand that aquatic plants and algae both need light and nutrients to survive. When you see a beautiful planted aquarium with thriving aquatic plants and clear water understand that the tank is not algae-free. Every surface including plant leaves has a thin coating of algae, bacteria, worms and other microscopic life. The clear-looking water is actually teeming with algae cells. In this situation algae growth is nicely balanced with plant growth. It is not possible or even desirable to eliminate all algae growth in a planted aquarium. Algae are an important part of the food chain in an aquarium and are also helpful in maintaining a healthy biological balance that ultimately results in a beautiful planted aquarium. There is also evidence that actively growing aquatic plants release compounds that inhibit algae growth (Allelopathy), helping to maintain a proper ecological balance. There is also a natural order of appearance of certain kinds of algae as a new aquarium ages. Under normal circumstances different types of algae will appear and disappear as the aquarium matures and a balance of algae species takes hold. The key to minimizing algae growth is to create an environment that favors plant growth over algae growth. In general this means maintaining a steady carbon dioxide level and keeping the nutrients under tight control so plants thrive and algae starves.

Black Brush Algae (BBA)

One of the toughest algae to control, Audouinella is actually a type of filamentous red algae. It attaches to the edges of plant leaves, bog wood and aquarium hardware, forming dark, velvety patches. BBA will attach to filter outlets near fast-moving water or in poor water circulation areas of the tank. This algae will grow in dim and brightly-lit conditions. It is difficult to remove from plants and surfaces even when it is dead.

Prevention & Control

Trim off infested leaves when algae first appears

Take steps to maximize plant growth which inhibits the algae

Treat the water with higher doses of liquid carbon (glutaraldehyde-based) additives

Provide a stable CO 2 level so plants grow at a steady rate and out-compete the BBA

level so plants grow at a steady rate and out-compete the BBA Stock the aquarium with Siamese algae eaters

Blue-Green Algae

There are many species of blue-green algae (BGA) that can appear in your aquarium. Anabaena, Aphanizomenon, and Microcystis are common types. BGA is technically a photosynthetic bacteria called Cyanobacteria. It thrives in nutrient-rich water and can live in low-light conditions. BGA may appear in newly set-up tanks during the break-in period or later in dirty, poorly maintained aquariums. Normally it fades away as the new aquarium matures.

Prevention & Control

BGA can appear in newly set-up tanks

Siphon out the algae while making water changes (approx. 30%)

Increase water circulation to prevent stagnant areas

Increase nitrate to about 20 ppm if using the Estimative Index method

Keep the gravel bed free of decaying sludge and organic matter

BGA should disappear in a clean, healthy, well-lit planted aquarium

If BGA persists, use an anti-bacterial medication that contains erythromycin

Blanket weed (Cladophora)

There are many species of Cladophora that are grouped into the blanket weed category. Blanket weed is a branching green filamentous algae. The algae can form free-floating mats or attach to bog wood, gravel and plants. It thrives when nutrients in the aquarium water are elevated. Cladophora gets its carbon from either bicarbonate (alkalinity) or CO 2 and can thrive even if CO 2 is low. Higher doses of glutaraldehyde-based carbon supplements can help control blanket weed.

Prevention & Control

Make sure new plants are free of blanket weed

Maintain proper nutrient and CO 2 balance to stimulate plant growth

balance to stimulate plant growth Manually remove clumps of blanket weed

Amano shrimp and Cherry shrimp will graze on blanket weed

Diatoms – Brown algae

Diatoms are single celled algae that can appear as a brown coating on aquarium glass, gravel and plant leaves. There are many species. Diatoms form a silica cell wall called a frustule. The silica is extracted from the water to form the hard “skeleton”. Diatoms are usually one of the first types of algae to grow in a new aquarium, appearing on the glass and gravel. As the tank matures diatom growth usually declines and becomes unnoticeable. Diatoms may coat poorly growing plants and dying leaves. If your tap water is high in silicates it may cause excess diatom growth.

Prevention & Control

Diatoms normally disappear over time

Wipe the aquarium glass with a soft cloth

Add a school of Otocinclus

Green dust algae

This algae looks like a fine green layer of algae on glass and bogwood. It is unsightly and requires frequent scraping to keep the glass clean. The cause is a simple imbalance in the competition between aquatic plants and algae for nutrients and light. A lack of a single nutrient, like nitrate or phosphate, can inhibit plant growth and tip the scales toward green dust algae. Too long of a photoperiod can also stimulate this kind of algae.

Prevention & Control

Keep the lights on for no longer than 10 hours

Use a balanced fertilizer regime

Scrape the glass with a razor or algae scraper

Maintain a steady CO 2 level especially in a high-light aquarium

level especially in a high-light aquarium Add a Bristlenose pleco or school of Otocinclus

Green spot algae

Green spot algae form small colonies of single-cell algae growing on plant leaves and aquarium glass. The green spots can be difficult to scrape off the glass. The colonies of green algae can appear on the leaves of slow-growing aquatic plants. Slow plant growth and having the lights on too long can allow green spot algae to take control.

Prevention & Control

Trim plant leaves if they start to decline in health

Encourage plant growth by maintaining a stable CO 2 level

level Increase phosphate level (Estimative Index method) if necessary to stimulate plant growth

Add a Bristlenose pleco or school of Otocinclus

Green water algae blooms

Green water is caused by explosive growth of single-celled green planktonic algae. The algae cells quickly reproduce until the water turns green. Eventually the algae will die back as nutrients become depleted. A sudden die-off can cause a low oxygen condition that results in fish loss.

Prevention & Control

Green water blooms may disappear after one to two weeks

Keep the lights on for no longer than 10 hours

Turn off the aquarium light for a few days to trigger an algae decline

A UV light will kill the algae and prevent its return

Hair algae

Hair algae are green filamentous algae that grow in long strands. Hair algae can clog filter intakes and become entangled in aquatic plants. Like blanket weed, hair algae thrives when it has adequate nutrients and aquatic plant growth is slow.

Prevention & Control

Keep the lights on for no longer than 10 hours

Physically remove or siphon out the algae strands

Flagfish or Mollies will eat hair algae

Cherry and Amano shrimp will graze on hair algae

Staghorn algae

Compsopogon is a red algae that appears green, white or gray in color. It has a branching growth pattern that resembles an antler. Staghorn algae can attach to equipment and plant leaves. It is believed that a nutrient imbalance or low CO 2 allows it to thrive.

Prevention & Control

Manually remove the algae from plants and equipment

Maintain proper nutrient balance

Aquarists report success with Siamese algae eaters

Fuzz Algae

Filamentous algae species look like fuzzy green strands. Fuzz algae can appear when nutrients are high and plants growth is low due to CO 2 limitation. Fuzz algae can also grow when there is a nutrient shortage and aquatic plant growth is inhibited.

Prevention & Control

Manually remove the algae

Maintain proper nutrient and CO 2 balance

balance Treat the water with higher doses of liquid carbon (glutaraldehyde-based) additives

Add Amano shrimp, Cherry shrimp, Rosy barbs or Mollies

Algae Clean-up Crew List

These guys may be a temporary fix to some of your existing algae problems. However, note that you should never rely completely on these critters to control your algae. The key to beating algae is a balance of proper water parameters, light, and CO2!

Otocinclus

Diatoms

Green dust algae

Green spot algae

Hair algae

Siamese algae eater

Black brush algae

Nerite snails

Diatoms

Green dust algae

Green spot algae

Amano shrimp

Hair algae

Blanket weed algae

Fuzz algae

Flag fish

Black beard algae

Hair algae

Blanket weed

Mollies

Hair algae

Blanket weed algae

Fuzz algae

Rosy barbs

Black beard algae

Hair algae

Blanket weed algae

Fuzz algae

Bristlenose pleco