Understanding Aquarium Algae

What is Algae?

Algae are a type of plant species. With that said, they also consume carbon dioxide and nutrients. Their growth gives a dirty and murky appearance to the aquarium.

In bodies of water, there are different types of algae. In order to know how to control their growth, you should know what types of algae are present in your aquarium. Green coloured algae are the most common type. These indicate good water quality. Green algae are considered as “good” algae, but their growth should be kept under control so they won’t deprive the fishes of nutrients. Some aquarists let green algae thrive to serve as a dietary source for their fish. There is a type of green algae that grows quickly; it can turn the aquarium water green and murky. High light levels are conducive for their growth. This type of algae is good for raising brine shrimps.

Hairline algae seen under microscope at 100x enlargement.
Hairline algae seen under microscope at 100x enlargement.

Blue-green algae have a similar appearance with green algae but unlike green algae, blue-green algae indicate poor water conditions. They are actually not a plant species, but rather cyanobacteria. They usually grow in sheets and emit a musky odour. They indicate excess light, high amounts of organic waste and phosphate in the aquarium water. If neglected, they can form a thick layer of foam. Overfeeding and poor aquarium maintenance also contributes to their growth. Cyanobacteria can also appear black and brown.

Algae on a piece of driftwood
Algae on a piece of driftwood

Brown and red coloured algae may indicate problems in the aquarium’s ecosystem. Saltwater and newly set aquariums are usually troubled with brown algae because of the chemical make-up of the water. It could be that the phosphate levels are too high. Brown algae indicate high silicate levels and low light levels. Don’t mistake green and brown algae with diatoms which are microscope organisms that form circular, calcium secreting populations that serve as a breeding ground for algae. Diatoms are hard to remove, unlike brown and green algae.

Staghorn algae resemble clumps of hair. They grow in a branching manner, thus the name. They tend to grow around aquarium equipment such as filters. They are hard to remove mechanically but they easily come off with bleach.

Fuzz algae usually grow on plants and aquarium decorations. They resemble 3mm long strands and barely affect an aquarium’s appearance and nutrient content. They can easily be kept in control with algae eating fishes. A virulent form of fuzz alga can be called beard alga. Beard algae are half a centimetre in length and grow in thick swathes. They aren’t a sign of poor water quality but their fast growth rate makes them undesirable. Another similar looking alga is the hair alga. It grows on the sand, gravel and base of aquatic plants. It doesn’t form ripples with the water’s current, unlike fuzz and beard algae.

Lastly, there’s the thread alga. It grows up to 12 inches or 30 centimetres long and is composed of fine thin strands. It doesn’t form thick patches. These algae are an indication that the iron levels are too high. They can be mechanically removed by a toothbrush.

Where Does Algae Come From?

Algae are organisms that are considered as plants because they undergo photosynthesis. With proper light, nutrients, temperature and carbon dioxide, they can multiply quickly.

How can you control aquarium algae?

You cannot completely eliminate algae, but you can control their growth. Most kinds of algae proliferate due to light. Depending on the type of algae indicated above, you can either limit or increase light exposure. Sunlight in particular accelerates algae growth but decreases brown algae. Ideally, aquarium with plants should receive 10 hours of light daily and those without plants should only be exposed to light for 6 to 8 hours.

Clean the aquarium water periodically, depending on how many litres of water the tank holds. Make sure to also clean your aquarium filter as often as you clean your aquarium tank. Feed your fishes only three times a day so disintegrated food won’t contribute to excess phosphate and ammonia levels. Test your water to check if the phosphate, ammonia and nitrate levels are too high.

Scrub the glass walls, aquarium equipment and decorations. You may use a toothbrush to get into tricky corners, an abrasive sponge or a special algae scraper. If your aquarium is relatively big, you can buy algae cleaners with a two-way magnet so you can clean the algae from the outside of the aquarium. Soak the gravel and sand in algae-control products and wash them thoroughly. For algae that can’t be removed mechanically, apply the appropriate algae-control solution.

Which  product  do we recommend? Without a doubt, Algae Control by Tetra. It’s cheap, and it does the job every single time.

Shrimps and Fishes that eat algae

Certain shrimps and fishes feed on algae. Amano shrimps are the most common freshwater shrimp used to control algal growth in aquariums. This shrimp species also feast on dead plant leaves. They even carefully sift through aquatic plant leaves and sponge filters in search for algae.

Amano Shrimp [Caridina multidentata]
Amano Shrimp [Caridina multidentata]

Cat fishes are commonly used to control algal growth. Cory cat fish does a good job of eating not only algae but also bits of fish food that have settled on the gravel. Plecostomus or plecos cat fish is a good choice if you have a large aquarium. Take note, however, that large plecos tend to eat the leaves off aquarium plants along with the algae. Otocinclus or otos are 2” long cat fish species that make a good algae-busting tandem with algae eating shrimps. If you don’t have that much algae, it’s best to supplement cat fishes with vegetable-based fish food.

Black mollies, Siamese algae eaters and peckoltia prevent excessive growth of fuzz algae. Siamese algae eaters are also excellent for preventing excessive red algae growth. When buying algae eating fishes, it’s important not to feed more than once a day if your aquarium tends to accumulate algae very fast, otherwise they would ignore the algae.

If you are interested in learning more about algae eating fish, then check out our list of the best 12 algae eaters.