Fight filamentous algae in the aquarium

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Fight filamentous algae in the aquarium: algae

String algae are widespread in aquariums and can proliferate in masses. When it comes to an escalating growth, these aquatic plants quickly become an unwanted plague. Filamentous algae are often found in the aquarium where too much light hits the surface of the water and there are too many nutrients in the water. With the right countermeasures, however, further expansion can be sustainably prevented.

General information

Algae are one of the oldest aquatic plants on earth, so over time, different varieties have developed, which occur in all waters. Therefore, it is virtually impossible to get the aquarium completely free from algae. To some extent, filamentous algae are useful and serve as a food source for the inhabitants of the aquarium. Under optimal conditions, thread algae in the aquarium can proliferate extremely strongly and have a visually very disturbing effect. In addition, these aquatic plants form lumps that can lead to clogged filter systems. In addition, small fish and other microorganisms can get caught up in these clumped-up areas and subsequently die.
  • Thread algae are undemanding and easy to care for
  • Are strongly colored green
  • Form up to 20 cm long threads
  • Will be dragged by the water flow in the length
  • They often grow in the form of weedy cobwebs
  • Over time, form dense and nationwide carpets of fiber material
  • Also often dive as small, green cotton buds
  • Some are only kurzfädig with lengths up to 5 cm, in tufts and furry
  • Usually arise in clear water
  • Prefer alkaline pH in the water

Causes & Symptoms


There are several causes of excessive growth of filamentous algae. These appear quite often in the initial useful life of an aquarium, since the water chemistry has not yet developed optimally. In addition, this species of algae is in the early days enough space for the spread available, if so far no other aquatic plants were settled. Furthermore, erroneous nitrate levels and imbalance in nutrients accelerate the growth of invasive filamentous algae. The light conditions are also often the trigger for a sprawling growth of algae. Filamentous algae often settle on decorative objects and prefer sites with a uniform flow of water, so they are often found on the water filter outlet.
  • Too few aquatic plants in the aquarium
  • Too many nutrients in the water due to too much fish food
  • Too little or too much carbon dioxide in the water
  • Too low or too high nitrate levels
  • Too few inhabitants, fish and invertebrates are missing
  • Too many residents also lead to imbalance in the aquarium
  • Too much illumination with too long illumination times
  • Intense sunshine through windows on the aquarium
  • Missing or faulty filter systems
  • Too small aquarium with too little water volume


A quick and convenient way to remove the thread algae is by manual fishing. This should not happen with your hands so as not to unnecessarily contaminate the water. Better are previously cleaned objects, where the thread algae get stuck and so are easy to fish out. To avoid an imbalance in the nutrients in the aquarium, the fish living in it should not be over-fed. A great help in combating the causes is the determination of water quality. This value can be determined with a strip test or an electronic measuring device, both can be obtained from specialist dealers. If the water in the pool has been tested, then a water change is usually due.
  • Seek filamentous algae mechanically
  • Helpful are wooden skewers or thin bottle brushes for winding
  • Scrub stones and decorative objects with a brush
  • Also remove any remaining algae
  • Have at least one day off per week
  • Avoid too hard and alkaline water
  • Instead of tap water, use better collected rainwater
  • Plant the aquarium correctly
  • Do not locate slow growing aquatic plants
  • As inhabitants use algae-eating fish and invertebrates
  • Too high CO2 levels due to increased oxygen supply
  • Water purified by osmosis filters positively changes nitrate levels

water change


A regular water change is not only essential in the destruction of algae, but also important for the ecological balance in the aquarium. In this process, not the entire water should be replaced, but it is only a certain percentage of the old water supply to replace with fresh water. In this way, the natural water chemistry in the basin remains intact.
  • Exchange 30 percent of the old water once a week
  • In case of extremely heavy infestation, replace water 2 to 3 times a week
  • Ideally, use osmosis-filtered water
  • Tap water often has incorrect pH
  • Test pH before use
  • Pre-treat water accordingly

Change in lighting conditions

If too much light falls on the aquarium, then both the water temperatures and the chemical composition of the water change. Therefore, it is important to ensure adequate shading, especially during the midday heat in the summer.
  • Locations directly at the window are not ideal in the warmer months
  • In summer place the aquarium in a slightly darker place
  • During the midday heat, provide shade through blinds or blinds
  • Do not set the lighting in the pool too high and start it too long

Branch from the willow tree

An effective and simple measure to combat the filamentous algae are branches of the willow tree. These release certain chemicals to the water and thus prevent the further spread of the invasive aquatic plants.
  • Acetylsalicylic acid of the branches stops the growth of algae
  • Break off a few branches from the willow tree
  • Make all leaves before
  • Place branches at several locations in the aquarium

Natural predators

Catfish aquarium

As an animal countermeasure, there are certain aquarium inhabitants who feed on the thread algae. These include, above all, the voracious snails. However, many owners of an aquarium have certain prejudices about the snails and fear that they will not only eat the filamentous algae, but also the other and useful aquatic plants. These fears are completely unjustified, as most snail species are not able to do so due to too soft mouthparts. The snails listed below only eat foul fruit, soft thread algae, and leftover food left over from the fish. In this way, the snails maintain a healthy balance in the pelvis.
  • Posthorn snails, snail snails, blue and golden apple snails are ideal
  • Even dwarf shrimps are in continuous use in algae destruction
  • 30 pieces are suitable for a 300 liter tank
  • Salmler, flag cichlids, Siamese weevils and Harnisch catfish also eat algae
  • Even densely vegetated areas are eaten so bare again
  • Aquarium becomes naturally algae-free


If the algae attack over, then grab many owners of an aquarium to chemical agents. However, these should only be used in an absolute emergency, as this significantly disturbs the ecological balance. The stronger the means and the faster they work, the greater the danger to the other aquatic plants and the inhabitants of the basin. For these reasons, biological agents are preferable.
  • Chemical agents quickly kill thread algae
  • Although water is clean, but it comes to imbalance in the pelvis
  • Better are biological means on a natural basis
  • String algae and AlguMin are effective
  • Fermented cereals are also biologically acceptable
  • Alarming are algae killers based on fruit acids
  • Citric acid destroys the cell structure of the algae and leads to their death
  • But then the acid becomes a fertilizer, the phosphorus content increases
  • Following the thread algae grow stronger than before
  • Gills of some fish species are damaged by fruit acid compounds

Video Board: How To DESTROY Algae in 30 Seconds (Get Rid Of Aquarium Algae FAST).

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