Algae in the aquarium might be the greatest nuisance for every tank keeper, be it in a classic social tank, an aquascape, a biotope aquarium or in breeding tanks for fish or shrimp. When confronted with an algal infestation, many aquarium keepers simply give up their beautiful hobby. However, there are good ways to get a grip on these pests, to fight them off or to prevent them from spreading.
What are algae?
The term “algae” is basically a comprehensive term for a vast number of different organisms. All plants not belonging to the mosses (liverworts, true mosses and hornworts) or the higher plants (ferns, Lycopodiopsida and seed-bearing plants), are classified as algae. Amongst them we have microscopic unicellular organisms and thread-like forms as well as the so-called macroscopic algae, like seaweeds, some of which can reach a length of up to 60 meters. For life on Earth, algae are crucial.
Just like germs, i.e. viruses, bacteria and other microorganisms, the smallest algae forms are omnipresent in our environment. There are some algae that float in the air passively, the so-called aeroplankton, in order to reach new places to inhabit. For our aquaria, this means that their omnipresence makes an aquarium that is absolutely free from algae practically impossible.
The aquarium plants need to be supplied with the full range of nutrients with a suitable fertilising regimen, which is crucial. Of course, the nutrient supply should not only be balanced but also needs to be adapted to the situation. For example, plants do not need as high levels of micronutrients (iron and trace elements) during the cycling phase of the tank as later on when the plant mass is larger. During the first weeks in the life of an aquarium you should therefore adapt your fertiliser regime and your lighting hours to the situation. For the cycling time in a new aquascape or planted tank, we recommend the following:
A CO2 content of around 20-30 mg/l, measurable by a permanent test with test reagent
10 to 25 mg/l of nitrate (NO3)
5 to 10 mg/l of potassium (K)
0.1 to 1 mg/l of phosphate (PO4)
add only 1/3 of the amount of iron fertilizer recommended by the manufacturer
>10 mg/l of magnesium (Mg)
Only switch on the lights for six hours in the beginning. When the biological system in the tank runs stable and without problems you may increase the daily lighting time by half an hour per week. Under moderate to strong light, you are aiming for a daily lighting time of 8 to 10 hours, under less strong light, a longer phase of 10 to 12 hours is recommendable. With the help of our light calculator you can easily find out which category (low/medium/strong) your lighting system is in.
When the aquarium plants start growing their nutrient requirements will increase, so you will have to adapt your nutrient supply to their growing needs. You can find more detailed information in our article “fertilization during the cycling phase”, which treats just that subject.