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Algae in the aquarium: your ultimate guide to an algae-free aquarium

Do you also have algae in the aquarium? What do you ask yourself? With the help of this article, you can find out what type of algae it is and what is the cause. And above all, what helps against the algae in the (freshwater) aquarium!

So learn in the following sections how to identify and, above all, remove!

But let's come back briefly to the general classification and definition:

What are algae?

In order to give you a rough insight into the science of algae, the phycology, I will briefly explain to you, what algae are and what distinguishes them from plants in the aquarium.

There are countless different types of algae - fortunately, it is a bit more manageable in the aquarium. Many of the green crooks can only be identified exactly on closer inspection.

In total there are tens of thousands of subspecies of algae species, only a few of which are interesting for our beloved freshwater aquarium. There are those Algae extremely adaptablewhich probably gave rise to the innumerable species. Another reason why it is sometimes difficult to identify them.

But what exactly are algae?

According to the biological definition, they belong to the low aquatic plants. Just like normal aquarium plants, they consume nutrients from the water and convert them with the help of light and CO2 into oxygen and plant / algae mass.

Basically, you can compare algae in the aquarium with weeds in the garden. Both of these usually sprout very unintentionally and simply disturb the look of the bed and basin.

Algae in the aquarium: a love-hate relationship that even saves aquarium inhabitants!

No aquarium owner likes algae.

But the blatant thing is that this sometimes even help. Because only they transform a halfway unplanted aquarium into one for fish, shrimps and the like. in a halfway livable home. Without it, some of the aquarium inhabitants would be affected address high nutritional values ​​in the short or long term.

Some of the green, blue or floating algae that appear responsible forthat the water values ​​are considered “good” and without the algae the aquarium would literally hit the wall.

How do algae develop in the aquarium?

Algae do not just arise in the aquarium!

Algae are mostly already in spore form and not visible in the water and / or on furnishings and plants. That is also one reason why an algae-free aquarium is (almost) not possible, at least in the run-in phase.

Because especially at the beginning they have due to their adaptability clear advantages over plantsthat first have to put down roots or adapt to the underwater world.

Generally one can say that the unicellular algae are an indicator of this are that the plants are missing something in order to grow optimally.

Why do algae appear in new aquariums?

Algae in newly set up aquariums are completely normal, as the bacterial fauna first has to develop. As quickly as they came, they are fought again.

Another Reason for the algae to spread During the running-in phase of the aquarium, the choice of plants could fall back.

Often in the aquarium trade the plants obtained from nurseriesthat the enormous plant masses mostly over water to produce.

So the plants come from the nursery in their "above water" form (the emerse) in the trade and then brought to you in the aquarium. That's not a problem at first, because the plants change within a few weeks on the submerged form.

The so-called in-vitro plants, which are supplied in a very fine growth form anyway, are a bit behind in terms of development speed.

I still like them best!

Algae look for their gap!

Unfortunately, the algae naturally take advantage of this time gap have a certain head startbecause they don't have to get used to the underwater world.

I am currently setting up the running-in period for the aquarium rather too many than too few plants a.

Gladly also some that come from well-established aquariums anyway and no longer need to be changed.

Fast-growing plant species such as hornwort, waterweed or the beautiful Brazilian pennywort help prevent algae, especially in the early days of the aquarium.

You can find a list of fast-growing plants here: Fast-growing plants against algae.

A fertilization with a full iron fertilizer or even an NPK fertilizer is in my opinion in the run-in period after not necessary. I usually wait so long to fertilize until I have clear vegetation able to see.

In any case, a CO2 system is connected from the start. Also because this pushes the pH value in a plant-friendly direction (6.5 is in the optimal range for plants) and supplies them with the important CO2.

Just be patient

Some types of algae have one certain heyday and disappear just as quickly as they appeared.

For example, diatoms are very often to be discovered in the running-in phase of the aquarium. But they also mostly disappear on their own.

That's why you should have patience in the early stages of the pool and not drive you crazy about every little algae.

Regular water changes and close observationwhether it gets worse or better bring you to that algae-free aquarium a little closer.

Dr. alga

To loosen up the text, you can find a video from colleague AquaOwner on the topic here Fight algae in the aquarium:

Possible causes of algae in the aquarium

Especially the high ones or those that are not in equilibrium with one another Macronutrients, such as nitrate (NO3) are often causes for the appearance of algae.

Even densely populated aquariums tend to be quickly ingested by algae. Then the cause - in this case the high stocking and increased feeding - has to be corrected directly. A lot of food leads to a lot of excretionwhich in turn leads to a higher nutrient load.

You surely know clear waters in the great outdoors, which then begin to appear strongly greenish in summer or at the fertilization time of farmers.

Here, too, the nutrients flowing into the water through the groundwater (which in turn ensure better plant growth in fields) are responsible for this.

As each Algae specific causes I will only cover general reasons in this main article on algae in the aquarium.

Algae and aquatic plants are often in direct competition.

The green, blue, brown or partly red algae usually appear when a building block for good plant growth is not sufficiently present in the water or is completely missing.

Just missing CO2 is often called growth-limiting element seen for aquarium plants. In addition to carbon dioxide, the element light or a nutrient can also be the reason that limits plant growth according to the law of the minimum.

Algae from too much light in the aquarium

Without appropriate lighting Even the most undemanding plants will not be in the aquarium. Without sufficient light, they cannot produce oxygen through photosynthesis, nor can they counteract excessive nutrient concentrations.

If the aquarium is not lit, it will be there is a high probability that no algae will occur. Because both algae and our beautiful aquarium plants grow with the help of green chlorophyll, what light, Converts CO2 and nutrients into oxygen and (roughly speaking) growth.

Using an exaggerated example, I would like to briefly explain to you how important the right light is in the aquarium to prevent algae:

Imagine you only have a few slow-growing plants, such as Bucephalandras, Anubias or ferns, but you have a real floodlight system for lighting in the aquarium.

What do you think will happen to this strongly illuminated aquarium in which there are only a few slow-growing plants?

Exactly: Algae find their way and take advantage of that there are no fast growing competing plants gives! Green algae and thread algae in particular are very fast here and sometimes are already widespread within 2 days!

Too long lighting time promotes algae

The sun usually shines in nature only 8-10 hours and that's how I would personally adjust the aquarium lighting.

Aquarium owners tend to switch the aquarium light in such a way that they turn on the light in the morning before work and let it shine during the day until the evening while watching TV.

In purely mathematical terms, you are fast with 12 hours of light and more! That is clearly too much.

My tip for the optimal lighting time in the aquarium:

First turn on the light in the aquarium so that you can still benefit from the illuminated aquarium in the evening or generally after work.

In the morning I leave the aquarium out completely, so that I can relax and enjoy the shrimp, fish and the like until 10 p.m. can observe in light. And that without going through algae caused too long lighting time to be disturbed!

Does a break in lighting help minimize algae?

If you would like to have the aquarium illuminated in the morning before work, you can use a so-called Lighting break think. This is like a lunch break that helps the plants to recover from light stress.

You can illuminate the aquarium for a total of approx. 10 hours and a lighting break of 3 to 4 hours is inserted in the middle. During this time, the CO2 should definitely be switched off as photosynthesis stops and the plants need oxygen.

I can't say whether the lunchtime lighting also helps against algae. But it does reduce the light stress of the plants and can give them a growth advantage.

Aquarium plants need a certain amount of time to come to rest from full speed or full lighting. Therefore, the lighting break should definitely be 3–4 hours. If the aquarium is illuminated for 4–5 hours before and after the lunch break, this should be a good value.

So: The aquarium light is on for 4 to 5 hours, followed by one 4 hour lunch break with the lights switched off and then the light burns for another 4 to 5 hours into the evening.

I can also provide you with a concrete extreme example here:

After moving house, I once accidentally set the timer that was linked to the aquarium light permanently all day had switched on. So this aquarium was approx. For 2 weeks, unnoticed by me, 24 hours illuminated.

Who do you think got the upper hand here in the aquarium?

Exactly: the algae spread strongly. Especially green thread algae spread out and vegetation was almost barely recognizable. The reason for this: plants can under so-called light stress Suffer.

This light stress can get through too little, but also through too much light in the aquarium and lead to the fact that the biochemical processes in the leaves of the plants no longer function properly. In the long run, this can even lead to The death of the aquarium plant.

Special tubes that make plants grow and decimate algae

There are always times The rumorthat with certain light it would be possible to help plants grow and to disrupt algae as they grow.

I would like to remind you once again that algae and the higher plants are very similar in structure. In my opinion that speaks a lot against the thesis that certain fluorescent tubes help against algae pests. So don't let this drive you crazy!

I like to use a light temperature of 4500 to 7000 Kelvin for fresh, clear light close to daylight.

Everything that is well over 7000 Kelvin slowly turns bluish and is often used in sea water. Everything below 4500 Kelvin turns very yellow very quickly and makes the aquarium look a bit dim, in my opinion.

LED lighting leads to strong algae growth

Just like the thesis in forums, aquarium facebook groups rumored that there are some There are lights that decimate algae, it is also often read that the very modern LED lighting means that algae occur more frequently.

I can actually confirm this by observing the various forums and groups.

You may also ask yourself the question ...

... why is it that aquariums with LED lighting tend to have increased algae growth?

The reason for by the new LED lighting caused algae plague is mostly that the Lumen number of the LEDs clearly above those of the old fluorescent tubes.

To clarify the reason for the algae spreading in the aquarium, we can think of the aquarium lighting as a car.

You are figuratively speaking when changing from old dim T8 or T5 tubes to modern LED lighting, from an Opel Corsa A (not against Corsas, I drive one myself :)) to a chic sports car switched with real power.

The sports car drives faster, but of course also drives faster against the wall.

Stronger lighting can carry algae with it!

I mean to say that when the lighting is stronger, you shouldn't just let everything run unobserved as it did before. An adaptation of the fertilization is inevitable with strong LED lighting and helps to give the plants everything they need to grow. So the algae don't stand a chance and you can prevent them well.

The aquarium now moves significantly faster, so to speak, due to the increase in light intensity (lumens).

Most of the time you also have to fertilize with a CO2 system and, above all, keep an eye on the macronutrients such as nitrate (NO3), phosphate (PO4) and potassium (K), as well as micronutrients such as iron!

The sports car also wants to be looked after and, above all, checked! :)

Too much sun also leads to algae!

As mentioned above, the aquarium is easier to control if it moves more slowly or if it is not lit at full speed.

This is exactly what can happen if too much sun or daylight falls into the aquarium due to the wrong aquarium location. Then a lot of lumens of light intensity come together very quickly, which just as quickly leads to uncontrolled algae growth.

So: it's best to choose a location for your aquarium that excludes direct sunlight and is not illuminated too much due to daylight.

This small requirement, as far as the location of the aquarium is concerned, is not only related to the solar radiation, but also to the heat development in midsummer. So you can see that everything speaks for a well-chosen place for the pool!


The water change as 1st aid in the fight against algae

In my opinion, changing the water in the aquarium is the key to algae control.

On the one hand, you can suck off algae carpets very effectively with the hose every time you change the water. And on the other hand, you compensate for any imbalance that may have arisen, which leads to a limiting factor for the growth of the aquarium plants.

Danger:You should be aware of the approximate water values ​​of your tap water! In some regions there is, for example, more or less nitrate in the tap water.

These values ​​are important to declare war on algae:

  • Nitrate (NO3)
  • Phosphate (PO4)
  • Potassium (K)
  • Iron (FE)

If you now have a high nitrate value in the tap water, that cannot be the limiting value and additional fertilization is not necessary here.

But if, for example, there is no iron in tap water, you can be sure that you should fertilize it.

That all sounds very theoretical, but it levels off over time.

Remove the basis of life from the algae by changing the water!

As already mentioned, the light or lack of or incorrect fertilization of the aquarium is often blamed for the cause of the algae plague.

But you often forget to ask yourself how you can counteract the respective factor.

Excessive nutrient concentrations in particular can be minimized relatively easily by changing the water generously (50% and more). In addition, the corresponding type of algae should first be identified.

The water change also brings new micro- or macronutrients into the aquarium, which the weakened plants may lack to continue growing.

You can only fight the cause of the respective alga by identifying it - because they are based on various different grievances.

A wrong approach to algae control can even lead to more algae spreading and defeating plants that are already blocked in growth.

Does a CO2 system help against algae?

In general, you cannot answer this question with a yes. What the CO2 system helps for, however, is the vegetation.

Plants, like algae, make their cells partly from carbon.

Where do they get carbon from? Usually the nitrifying anaerobic bacteria in the aquarium produce some carbon dioxide, which is enough for some plants to grow, but this source quickly dries up.

That is why the CO2 system was invented. With the CO2 system in the aquarium, you can achieve CO2 values ​​of approx. 20 mg per liter and thus prevent the so-called biogenic decalcification from taking place and not literally calcifying your plants.

Biogenic decalcification only occurs if the plants in the aquarium cannot find enough free CO2 in the water and thus remove the carbon that is important for growth from hydrogen carbonates. You can recognize the plant calcification by the really white leaf edges. It is not conducive to the overall metabolic activity of the plants.

You've slowly gotten over the general banter about the annoying greens. Now let's get to the topic ...

... determine algae in the aquarium

Which algae in the aquarium are you struggling with at the moment? The best thing to do is to simply compare your algae with those in the overview below.

Regardless of the type of algae you are dealing with, these 4 steps will help you fight algae:

4 important steps in the fight against algae in the aquarium

  • Identify algae: Only as soon as you are sure which alga you have in the aquarium can you investigate the cause. Because every algae plague has its specific trigger that has to be found!
  • Initiate first aid measures: a generous change of water together with the mechanical removal / collection of coarse algae accumulations help the plants "to get going again".
  • (Use unskilled workers: Please only use animals to combat algae if you have dealt with their keeping conditions and do not see them only as a cheap algae agent!)
  • Find out the cause: Have you identified the insidious alga? Then you can start to tackle the plague by the roots and balance the cause (see the detailed articles on the algae species in the aquarium below)

Which algae in the aquarium?

Which algae you have exactly in the aquarium is the initial question that you have to ask yourself.

In the detailed articles on the individual types of algae, which I gradually publish here, you can read why the respective type of algae occurs - i.e. what its causes are. And above all, what you can do about the respective algae!

The overview for identification: These algae are found in the aquarium

In the following overview you will find the answer to the question of which types of algae are in the aquarium. This should first help you to identify the nuisances and then to find out.

In the respective detailed articles, I usually proceed according to the same scheme:

  • Identify algae: is this the right alga?
  • Research into the causes of algae: why does the algae originate?
  • Quick help: In addition to first aid actions, I also go into possible home remedies for the algae
  • Remove algae: How do you remove and fight the algae in the long term?

Diatoms / brown algae

Similar to blue-green algae, the diatom (Diatoms) Brown, greasy deposits on plants and decorative objects in mostly newly built aquariums.

Even if it is obvious: Please do not name diatoms brown algae, even if the appearance of the diatoms suggests it.

The diatoms also like to settle directly on the substrate and are very easy to remove from panes etc.


Blue-green algae / cyanobacteria in the aquarium

Blue-green algae are actually more bacteria than algae and are also known as cyanobacteria. Blue-green algae appear in the aquarium as greasy blue-green surfaces and lie like a film over plants and furnishings.

In the article on blue-green algae you will find everything you need to know about cyanobacteria. Above all, how to remove the blue-green algae before you really have to do a dark short.


Brush algae

The name says it all: brush algae look like small black or reddish tufts of hair that are only 1 to 2 centimeters long.

During the run-in period, they like to spread out over furnishings and rather slow-growing plants and sit on the edge of the leaf.

The brush algae are very robust in terms of mechanical removal, but with a little time and the tips you can find in the article on the brush algae in the aquarium, you will get rid of them.


Thread algae

You can easily recognize thread algae in the aquarium by their name-giving shape: they look as if green threads are hanging in the aquarium. They are quite easy to remove mechanically.

In addition to collecting with the help of a wooden stick or toothbrush, you have to get to the bottom of the cause, as always.

In the thread algae article, you can read why thread algae developed and how to get rid of them.


Hair algae

The green hair algae look relatively similar to the thread algae, but grow a bit bushier and stockier.

Thread and hair algae like to appear together, the algae doc was able to observe. Especially new aquariums are her goal!

The clump of hair algae can be easily removed from the drain - er, I mean - aquarium by simply vacuuming it off.


Point algae

The very small point algae occur especially in aquariums with a lot of light.

You can usually find the dark green spot algae on the aquarium glass and on stones or, for example, slow-growing plants such as Anubias.

A very easy to contain algae that does not occur over a large area, in my opinion. All information and ways how to get rid of them can be found in the article on spot algae in the aquarium.


Floating algae or bacterial bloom

The floating algae make it really cloudy in the aquarium.

The type of algae belonging to the green algae is often introduced by a few spores and can make life really difficult.

Besides the causes of the floating algae that is really difficult to control, you will also find the heavy artillery and paths that you have to drive up in the fight against the pending plague:


Dust algae