All you need to know about algae

Kaspar Horst

How to avoid problems with algae

There is good reason for us to take up the topic of algae. Many aquarists have abandoned their only recently begun hobby after only a short while because they could not cope with the algae plague. In most cases mistakes that lead to later problems with algae are committed early on during the setting-up stage of an aquarium. In reality, though, algae don't pose a problem in an aquarium if some basic rules of aquarium maintenance are followed.

Even if - for good reasons - we don't want algae in the aquarium, we should, however, at the outset show some respect for them. Once we better understand the nature of algae, we will accordingly be better equipped to avoid them.

Algae - the oldest plants on earth

About 3 billion years ago blue algae developed as the first plants. They are the oldest living organisms known to us containing the colouring matter chlorophyll, the green dye in leaves. This invention with the aid of which nutrients could be produced from light is one of creation's greatest. The appearance of blue algae was closely related to the development of the oxygen atmosphere. It produced the ozone layer which in turn reflected the deadly ultra-violet radiation, thereby enabling the populating of surface waters.

For nearly 25 billion years algae were the only plants on earth. Only about 500 million years ago did higher plants follow. During this endlessly long period the algae accomplished an ecological achievement for the progressive development of flora and fauna on earth that cannot be praised highly enough.

Algae are plants

The close relationship of algae with aquarium plants often makes combating algae - once they appear in large quantities - such a difficult issue. Many factors that damage algae are also detrimental to plants. That apart, there are many kinds of algae with differing influences on the aquarium. Some algae are more or less harmless in an aquarium, others are highly dangerous and once out of control can impact negatively on the living conditions of fish and plants in the aquarium.

Algae in an aquarium can seemingly develop on their own out of nothing. In reality, though, the reproductive seeds of algae are tiny spores, present in nearly every aquarium. They are introduced, for instance, with plants, with the fish transportation water, live food or contrasts with other aquariums.

It subsequently depends on the living conditions in the aquarium, especially for aquarium plants, if the algae situation reaches unpleasant proportions or not. This, on the other hand, is the chance for the aquarist to head off such a potential plague: optimum care and maintenance of the aquarium water with the purpose of enabling healthy growth conditions for the aquarium plants will certainly prevent any influx of algae.

Algae are indicators for lacking water maintenance

It has unequivocally been proven that an infestation of algae will only occur if there is a specific nutrient deficiency, wrong lighting being applied or inadequate chemical water conditions being dominant in the aquarium. Also, an over-supply of nitrogen, especially in nitrate form, encourages algae because natural biotopes never reach such high nitrate values as can often occur in aquariums.

It is therefore entirely appropriate to formulate the basic principle that algae in an aquarium are an indicator that all is not right within the aquarium system. This can already be recognised by the fact that algae prefer to settle on sick or withered plant segments.

Algae and plants in competition for nutrients

In their billion year long development many algae have learnt how to survive under inhospitable living conditions. They utilise this advantage in an aquarium, for instance, when it comes to some sort of nutrient deficiency. As everybody knows the absence of a single trace element (iron, manganese amongst others) will lead to many aquarium plants ceasing growth. The algae's hour has struck. They are now at an advantage. It is therefore important to ensure an optimum and comprehensive nutrient supply.

An excess of certain nutrients, too, however, can be advantageous to the algae. In this case nitrogen in the form of nitrate and phosphorus play a deciding role. Aquarium plants have learnt from the outset how to extract and satisfy their nutrient requirements even from the most minute supplies of nitrogen in the water. In aquariums, however, they are often confronted with a hundred- to thousandfold supply of their natural conditions. The cause for these sometimes unfavourable conditions lies in the aquarium's structure. Many fish are confined to limited space, their "waste" chemically impacts on the aquarium water. Food scraps, too, rotting plants, black substrate as well as badly maintained filtration are responsible for this.

One remedy is a regular change of water (one third of the total volume every fortnight) coupled with corresponding water treatment and plant fertilisation.

Which kinds of algae exist in aquariums?

After what has been said so far it follows that there is no total one hundred percent prevention against the import of algae spores into the aquarium. Especially after the refurbishment of an aquarium do we have to be extremely careful. Here, too, the motto must be: beware the beginnings.

Harmless algae: brown and silica algae

It is entirely possible that we will notice a fine brown coating on the aquarium glass, perhaps also on stones, the thermometer etc. after only a couple of days into the tank's operation. In most cases these are silica algae. They are so-called pioneering algae that will later totally disappear again. These "brown algae", however, are easy to remove with a glass cleaner or a perlon wad. On the other hand they keep within limited numbers and automatically disappear once the plants have started to properly take root and optimum oxygen values are established in the aquarium.

Green algae

The green algae, too, can still be counted amongst the aquarium's harmless algae population. They are even considered an indicator for normal water conditions. They come closest to our aquarium plants.

Green algae in the aquarium indicate good water conditions, nevertheless they should not be tolerated. Photo: Michael Prasuhn

They are easily recognisable by their green or light green threads or sometimes their cotton swab-like webs. Despite this they should not be tolerated in an aquarium. They are also competing for nutrients with the aquarium plants. Getting rid of them is usually no problem. They can easily be removed by hand or by coiling them up on a small stick.

Green algae, highly magnified.

Dangerous algae

The algae mentioned below, however, should be taken seriously, their presence is not to be taken lightly. They can rapidly endanger an aquarium, especially when given time to settle in larger colonies.

Blue algae

They are to be listed first in the category of dangerous algae. They can be the first to appear in the initial phase of an aquarium. They prefer to exploit the situation when the whole aquarium system is not yet fully operational. They can be identified by their blue-green, sometimes brownish to blackish skinlike coating on leaves, stones, wood and substrate. They can also clearly be smelt, at times emitting a rather penetrating odour, when performing work on the tank or when syphoning them out of the water. Due to their slimy outer appearance they are also referred to as smear algae.

Blue algae usually start their growth on the aquarium floor, progressing to eventually cover the entire substrate with a slimy layer. Photo: Kurt Paffrath

In contrast to green algae, this variety signals alarm, an excess of nutrients is in the water - mainly nitrate and phosphate - , maintenance is lacking, plants are suffering.
Once detected they should quickly and repeatedly be removed with a siphon hose until totally eradicated. In most cases this task will only take a few days, only rarely will it be a protracted exercise. Fortunately these algae can be got rid of quite easily in this way.

Red algae

This is a whole group of algae, called beard algae, brush algae or bush algae by aquarists, depending on their nature as well as their outer features (see photos). They are so entirely undesirable in an aquarium because they are so especially difficult to get rid of. It is best to remove the whole leaf or even the entire plant, heart breaking as it might be. Particularly dangerous for the aquarium is their sudden and massive outbreak.

Macro photo of beard algae settled on a Vallisnerialeaf. Photo: Michael Prahsuhn

Beard algae are identifiable by their long, blue-green, dirty black-looking threads that grow especially on leaf edges. Leaf stems, edges of plastic items, wooden edges etc. are other preferred areas of settlement. They, too, should be radically cleaned out as soon as they reappear.

Beard algae on a Cryptocoryne leaf. Photo: Michael Prahsuhn

The so-called bush and brush algae also belong to the family of red algae. Common to them as well is their blackish, dirty green colour. Their actual red colouring is concealed, appearing when the algae are immersed in methylated spirits. They, too, like the beard algae, predominantly settle on withering leaf edges and stems, as well as stones, wood and plastic parts.

Effective ways to combat algae

To safely keep an aquarium free from algae there is a welltried and proven recipe. This recipe quite simply states: preventive action and optimum water maintenance. In more detail it reads as follows:

1. Right choice of location for the aquarium

Care should be taken that the aquarium is not exposed to direct sunlight. In most instances sunlight is too strong for aquariums. It delivers too much metabolic energy to the plants, they consume too many nutrients in the relatively small water volume, this will rapidly to a nutrient oversupply and thus growth will be inhibited. Algae are thereby advantaged.

2. Check plants prior to introduction

Don't purchase any aquarium plants from aquariums that contain algae. Inspect plants thoroughly, even at home prior to their insertion into the aquarium. Plants you have received from friends and other aquarists should also be checked for algae infestation and should be discarded if necessary.

3. Preparing pot plants for the aquarium

Aquarium plants bought in pots have generally been precultivated in plant nurseries. Plant leaves reach out of the water whilst the roots are dipped in special rich nutrient solutions which might contain lots of nitrate and phosphate.
This nutrient solution has in most cases not been completely rinsed out of the stone wool into which the plant roots are embedded. The plants should therefore carefully be separated from their pots and root substrate under rinsing luke warm water and only thereafter be inserted into the aquarium.

4. Optimum water treatment and regular water exchange

An optimum supply of aquarium plants with all essential nutrients, including trace elements, is a prerequisite for healthy growth with algae protection. Duplaplant, for instance, provides correct dosaging of macronutrients whilst daily Duplaplant-24 additives organise the correct supply of all necessary trace elements, including the all-important iron nutrient, for the plants. Through these well-balanced and separate supplies of macro and trace nutrients damaging over-dosaging is avoided, especially since many trace elements - if supplied excessively - are toxic and harmful to the plants, again handing the advantage to the algae.
A regular change of water (a third of the total water volume every fortnight) will provide for the removal of waste substances in the water and the harmful rubbish in the aquarium.

5. picstral pH-value through C02-supply

Adjusting the aquarium water to a picstral pH-value (6.8. to 7.2) provides not only for an optimum carbon supply to the plants but also for a good and life-enhancing chemical climate in the water. A valuable aid in accomplishing this aim are suitable C02-appliances, e.g. products by Dupla.

6. Adapted lighting

What do we understand by that?

Lighting above the aquarium must correspond with the aquarium's height and water volume. Reason: first, the light source must be powerful enough to provide sufficient light even for the mostly small plants on the floor of the aquarium. It is worth considering that most of the plants in the aquarium's foreground mostly grow on the embankment areas in their natural habitats, i.e. in a place with mostly good light conditions.
Light is energy for growth. This, however, also means that light has to be adapted to the aquarium's nutrient supply. Too much light rapidly leads to selected nutrient deficiencies, especially trace elements. This again would benefit the algae population. Too little light in turn leads to cessation of growth and lack of oxygen.
Within this border area correct lighting has to be chosen. For optimum aquariums this means: -Aquariums with a height of up to 40 cm: Tungsram FD-D 18 F84 or Osram Dulux DD 18/21 in the new Dupla Milux 60. -Aquariums with a height of up to 50 cm: mercury vapour lights 80/125W, e.g. Duplalux -Aquariums with a height over 50 cm: halogen metal vapour lights 70/150W as in Duplalux LI.

7. Preventive action through daily control

Especially in the start-up phase of an aquarium daily checks on algae build-up should be carried out. Layers of blue algae on the bottom or on roots as well as algae threads on leaf edges etc. should be removed immediately.

8. Prevention through algae-feeding fish

An effective measure against algae are fish that simply love to feed on them. A wide range of species is available for small to large aquariums. They don't, however, offer a 100% guarantee because these fish only too soon come to realise that dried foods taste far superior.

Here is a selection of proven algae-feeders:
* Feeder of beard algae: Crossocheilos sismensis (Siamese Flying Fox)
It is the queen amongst algae-feeding fish, especially when still young. Above all it particularly prefers the dreaded beard algae. Fully grown, however, it only measures 15-18 cm and should therefore only be used for small aquariums when young.

Due to good care, this aquarium shows no signs of algal growth: the Siamese barbel (Crossocheilos siamensis) prevents mainly the appereance of beard-shaped algae. Photo: Kaspar Horst

* Especially for small aquariums: Golden Otocinclus The small Otocinclus species is excellently suited for small aquariums. They rasp incessantly on leaves, stems and roots.

* Diligent and loveable: live-bearing fish Many live-bearing fish are algae-feeders as well. Amongst these we count the lively guppies, all derivatives of Poecilia sphenops, also called Black Mollies, furthermore all Platy kinds, Xiphophorus maculatus and X.variatus.

* Warning I must, however, issue a warning about one fish which is often recommended for algae prevention purposes: the Blue Bristlenosed Catfish Ancistrus dolichopterus. It works the algae to such an extent that it actually damages the surface of Echinodorus leaves (Sword species) until they drop off dead.

If more information or hints are required on algae-consuming fish, refer to Aquarium Today 3/83.

Other opinions, other ideas

As long as aquariums have been around there has been polemic and controversial debate in aquaristic circles on algae and their prevention. The question need to be put if here too all roads eventually lead to Rome, i.e. in this case to an aquarium free of algae infestation. The reply is clear and unequivocal: all unnatural suggestions and methods are to be rejected because they will eventually be detrimental to the aquarium's fish population and their success in combating algae is questionable at the very least.

I am mentioning this because I have in front of me a pamphlet titled "Algae problems" which could cause confusion especially with beginners. And since it is entirely possible that you too might receive this brochure, I wish to detail precisely why the listed recommendations should be rejected.

Daring and misleading advice

The following suggestions are given in the above-mentioned brochure:

• total height of substrate: 10-20 cm
• reductive slow-flow filter apparatuses
• hardly disrupt/stir water surface algae
• preventive additives
• water slightly murky
• little lighting
• midday break of 4-5 hours
• plenty of flaky foods
• oxygen, mornings: 2,5-3,5mg/1, evening: 3,5-6mg/l.

The underlying thesis for all these recommendations is quite obviously that oxygen in an aquarium is an evil (excrement) and has to be reduced. All the above advice reduces the oxygen content. Theses measures rigorously tamper with a basic law of nature. If one desires an aquarium with healthy and beautiful plants, provides it with essential lighting and the correct substrate and supplies it with all nutrient requirements, including C02, it is an unalterable law of nature that the plants produce oxygen and emit the excess amount of it into the water for the benefit of the fish population.

The brochure points discussed in detail:

A high substrate enhances the output of methane gas and hydrogen sulphide, the substrate will soon blacken. Consequence: loss of oxygen.

Correct is a substrate thickness, depending on tank size, of between 3 and 10 cm.

The recommendation to provide little light and have a midday break of 4-5 hours is particularly unnatural. It not only damages the algae but has an even greater impact on the plants. To turn a normal tropical day into two shortened days is an especially unbiological measure for the aquarium' s fish.

Correct instead is a lighting period of around 10 hours.

If feeding is excessive, rotting food will not only be a strain on the oxygen household but unwanted organic strains will also be brought about and also the algae nutrients nitrate and phosphate.

Correct is: only feed as much as can be consumed by the fish within a few minutes.

The suggestion to adjust carbonate hardness at 1-2°dH puts the aquarium within reach of an acid fall. The correct and optimum carbonate hardness value is between 4 - 8°dH.

An aquarium with an 02-content in the evening of only 3,5mg/ 1 is at risk - especially considering the multitude of reductive measures taken - of becoming void of oxygen at night, once all oxygen production has ceased: the fish will suffocate.

The reference to oxygen-poor waters in nature is incorrect. The aquarium is an artificial biotope with relatively little water. In nature a gigantic water volume will provide stability, even at low oxygen levels. This is not the case in an aquarium. That apart, in the tropics, too, there exist more waters with an optimum 02-content.

Correct instead is an oxygen content which measures around 5mg/1 in the morning.

I have covered this topic in Aquarium Today 3/92 in more detail.

A final word on chemical agents for combating algae. Insofar as they are based on the basis of growth inhibitors they consequently not only interfere with algae growth but also that of plants. It is tantamount to walking the edge in calculating a correct dosage so as to weaken the algae more than the general plant population. In most cases this will fail. If one inflicts more damage on the plants this again will benefit the algae.

Conclusion: only optimum living conditions for plants will guarantee an aquarium free of any algae.

Aquarium Heute 4/96