Combatting algae - here’s how it works
Algae can make your aquarium look very unsightly. They can overgrow your plants and decorations and restrict your fish’s habitat. But it is not that difficult to prevent or get rid of algae!
Why do algae grow in the aquarium and what can be done about it?
When algae get out of hand in the aquarium, there are always one or two causes. In this video, biologist Heiko Blessin explains very clearly and understandably why algae grow in the first place and what we aquarists can do about it. The topic of algae in the aquarium has never been explained in a simpler and more understandable way!
Why are algae a problem in the first place?
Algae belong in the aquarium as much as other water organisms. You can’t totally prevent their occurrence. As long as the algae growth remains low or it doesn’t noticeably gain the upper hand there is no need to worry. Strong algae growth, however, has a dramatic effect on the water: Algae are plants and produce oxygen during the day. But at night the situation reverses and the algae consume oxygen. With a heavy algae infestation the oxygen can drop into dangerous ranges at night and threaten the life in the aquarium. It is then advisable to aerate at night.
Exposed to light (during the day), the algae continue to consume carbon dioxide (CO2) like the water plants. This consumption can lead to an extreme increase in the pH level (pH > 9), which in turn leads to a life-threatening environment.
If the CO2 content in the water is no longer sufficient, algae are able to dissolve the CO2 out of the carbonate hardness (KH). The result is a decrease of this important water parameter which leads to an unstable pH level. The pH level drops significantly at night (to values as low as 4) and rises during the day to far too high values (up to values over 10), and this can mean the death of the aquarium dwellers.
Finally it is worth mentioning that dying algae are broken down by bacteria during oxygen consumption. Therefore the water needs to be aerated additionally when algae die!
Why do algae sometimes grow so much?
Algae are plants and grow especially strongly when lots of nutrients and light are available. With the help of water tests you can check how much of the main algae nutrients phosphate and nitrate are present. It is important for you to find out why such a strong excess of nutrients occurred. Mostly the cause is overfeeding, an insufficient partial water change or too high fish stock combined with too few plants.
Determine the food sources of the algae
Nitrate (NO3) and phosphate (PO4) promote the algae growth in the aquarium, if the following values are exceeded:
Nitrate: 5-10 mg/l ( JBL PROAQUATEST NO3 Azotany )
Phosphate: 0.1 mg/l ( JBL PROAQUATEST PO4 Fosforany Sensitive )
How to remove the algae nutrients
Scientific studies have shown that the phosphate/nitrogen ratio has a large influence on the algae growth. The ideal ratio for freshwater plants is 1:16 (converted to phosphate/nitrate it would be about 1:10).
Outside this range, which ranges from 1:15 to 1:30, the algae growth increases significantly, especially this from blue-green algae (cyanobacteria).
Do I have to use an anti-algae agent or is it also possible without one?
This is a good, justified question! If the aquarium is heavily algalised, a nutrient withdrawal is usually only helpful for a short time - and then the algae are back. The aquarium is tipped, like a scale, towards algae. It really helps to first use an anti-algae agent to tip the "scales" away from the algae tendency. Only AFTER you’ve used an anti-algae agent, will nutrient elimination via nitrate or phosphate removal work.