In a healthy well maintained aquarium algae is not usually considered a problem. No aquarium is completely free from algae but the degree to which it can quickly spread often labels it as a pest and therefore fish keepers must be aware of how to control it.

The most common problems with algae are that it can take over and kill plants and in large quantities can look unsightly. Additionally, an excess of algae sometimes points towards deteriorating water quality and therefore gives us an immediate concern for the health of the fish. Having said that, algae does have some benefits.

Algae gives an aquarium a rustic feel and should be as considered part of the natural decor. Some fish such as Ancistrus and Hypostomus catfish, the renowned Siamese Algae Eater (Crossocheilus siamensis) and Amano shrimps benefit by grazing on it and many fish keepers encourage algae in a sump filter, as its prolific growth makes it an effective nitrate reducer.

In newly set up aquariums, algae is a frequent cause of concern. In new tanks the filters are often not capable of processing all nitrogenous compounds effectively therefore, there is an abundance that allows algae to grow. Algae is quick to utilize light and carbon dioxide and can thus feed more efficiently on the nutrients present in freshwater than the plants, which take time to establish and root. The high nitrite levels in a new set-up mean that algae flourishes and grows faster than the plants thereby, consuming any nutrients before the plants can take hold. The net result being, algae flourishes and plants wither and die.

A common mistake in this case is to change the water but this can aggravate the situation by setting the cycling process back a few steps.

It is a better solution to ride out the cycling process, clearing algae as it grows and encourage the plants to grow, then to tackle any remaining algae in isolation. As the plants will eventually root and develop, they will feed on the same nutrients as the algae ultimately and out perform it.

Some plants can take months to establish in the aquarium but fish keeping is not a race so be patient. If algae at this stage is a concern, you can if you wish, ease the situation by growing inexpensive hardy plants such as Vallisneria sp. or Java Fern (Microsorium pteropus) and allow algae to grow on them. These plants will help to reduce the nitrogen compounds available to the algae and they can then be replaced over time as the aquarium matures.

As well as nitrogen, sunlight fosters algae. The positioning of an aquarium and use of correct lighting should alleviate this although this is sometimes easier said than done.

There are four types of algae commonly found in the aquarium and each type occurs as a result of distinct factors. Obviously, by correcting these factors, one will reduce the algae problem,

Blue Algae

Appears as blue-green and occasionally brown-black in colour. Blue algae is a definite sign of poor water quality and favours the bottom of the aquarium where water circulation is usually less rapid.

Blue algae becomes present when the substrate over fertilized or the fish have been over fed. It usually indicates that nitrate has risen to excessive levels greater than 200ppm (critical levels for fish). In a similar situation to the newly set-up tank infestation, as algae utilizes nitrogen quicker than plants they also flourish when nitrates rise.

Blue algae and can quickly kill plants if it grows on the leaves. This is because it is so dense that it prevents light form reaching the plant and quashes photosynthesis.

Unfortunately, Blue algae is not eaten by fish however, the cure is simple. Scrape the algae from any decor and remove affected plant leaves. You can then tackle the high nitrates via water changes.

Red Algae

Appears as red moss like growths on decor and more commonly as green threads or beards. Red algae is difficult to scrape off surfaces and not easily removed.

Red algae thrives in pH of greater than 7 and in water that is high in nitrate. Its presence also indicates a lack of carbon dioxide. As with Blue algae, Red algae can quickly become a nuisance and kill plants by blocking light and literally suffocating the leaves.

The cure for Red algae is to soften the water by filtering over peat. This also encourages plant growth as few species thrive in alkaline conditions. Flourishing plants help since photosynthesis becomes more effective increasing oxygen and reducing nitrate.

Brown Algae

Sometimes referred to as Gravel algae, Brown algae grows as a thin brown layer on the substrate. Its presence indicates inadequate oxygen, an abundance of nitrate and lack of light. Brown algae also points towards hard water (and thus potentially a pH greater than 7.0) in which plants tend not to tolerate.

To cure Red algae, apply stronger lighting. This can be easily be done by adding an additional fluorescent tube. This in turn, as with the cure for Red algae, will encourage plants to become stronger, increasing oxygen and reducing nitrate.

Green Algae

There are various types of Green algae but usually it appears as furry threads. Green algae usually turns water in to a green soup and like its relations can take over and kill plants. Some types of Green algae are introduced by live food, but it also occurs when fish have been overfed and too much light, particularly sunlight is present.

Green algae disappears if light is reduced, remove a bulb or shorten the lighting period, or if it receives no light at all for a few days. If the aquarium lighting is turned off a short period plants will not be harmed. Commercial products are available and can be effective against Green algae.

Green algae can also be removed with strong filtration such as using a diatom filter, or the introduction of Daphnia which feed on the algae. When the Daphnia have cleared the aquarium they in turn will be food for the fish.

Some types of Green algae only grow in clean water but water which is high in nitrate. This algae should be removed by hand and the nitrate corrected via a water change.

Algae Removal Tips

It is wise to adjust one thing at a time when curing any anomaly in the aquarium including algae. This way you can determine what has caused the problem and cure it.

• Identify the type of algae and refer to the section above.
• Remove as much algae by hand to give higher plants a chance to flourish.
• Reduce the lighting period, this can be quite drastic to periods as short as 8 hours. Alternatively, introduce a break in the lighting period.
• If using fluorescent tubes, ensure they are not too old (>18 months). An old tube can cause algae.
• Introduce algae eating fish. As well as those mentioned above, try Mollies or Dwarf Cichlids. Avoid the Otto, Otocinclus vittatus as this fish tends to prefer dried foods to algae.
• Check your water quality. In particular look for nitrite and nitrate.
• Check your tap water for phosphate. Phosphate is utilised by all plants and consumed quickly by algae. Phosphate may be undetectable in the aquarium because it is being used quickly by the algae.
• Look at the position of the aquarium. If it faces a window, sunlight could be the problem.
• Reduce feeding. Overfeeding causes high nitrate and poor water quality.