Jofre, Corydoras aeneus 1.0, marked as public domain, details on Wikimedia Commons
Diatoms form a brownish, greasy coating on the substrate, on objects and above all on plants and on the aquarium panes. Due to the photosynthesis of the diatoms, the surface is often interspersed with oxygen bubbles.
Because of their color, they are often referred to as brown algae. However, the name brown algae is incorrect, since brown algae live almost exclusively in the sea.
Only a few and rare species live in fresh water. Diatoms are also called diatoms and are unicellular algae that occur wherever water and light are present.
Examples are the sea, fresh water, forest floor and moss pads. They absolutely need silicic acid to build up their silicate shells.
Causes of diatoms
Diatoms usually appear during the start-up phase of an aquarium, when the bacterial cultures in the aquarium are not yet sufficiently developed and the plants used are not yet growing properly.
They are particularly common in dimly lit aquariums or settle in the shade of plant leaves or furnishings. But even with diatoms, illuminance seems to be only a secondary factor.
The essential role is also played by these algae oversupply of nutrients in the aquarium. Other factors, such as lighting, then influence which of the many types of algae will find the best conditions and, accordingly, will predominate.
Important: For the diatoms, silicic acid is a vital factor. If there is not enough silica, the diatoms die. Although silicic acid can often be found in tap water in various concentrations, over time it is converted in the aquarium through chemical processes into SiO2, which the diatoms can no longer utilize.
For this reason, diatoms often appear in newly set up aquariums and disappear by themselves after a few weeks.
In well-established aquaria, the silicic acid seems to convert more quickly, so that new additions by changing the water no longer lead to the appearance of diatoms.
In addition to a high concentration of silicic acid (H2SiO3), an excessively high phosphate value plays a major role in the spread of diatoms. Under such conditions, they also appear in well-established aquariums.
Some reports say that diatoms like to appear in aquariums with trocal tube lighting, sparse vegetation and harder water, i.e. typical perch tanks.
Measures
The first step is the clear determination of the water values, in particular the silicic acid and phosphate content. Unfortunately, quick tests are often imprecise here, so that a test kit is recommended even if they are a bit more expensive. Here we can recommend.
Alternatively, there are also separate ones silicate tests:
If the silicate value is too high, there are various granules that are used as filter material to determine the silicate content lower and remove the basis for the diatoms.
Reduce the silica content
© Mario Brown
If the water contains a high proportion of silicic acid, you can mix the water with water from an aquarium without infestation with diatoms during the start-up phase in order to reduce the concentration of silicic acid.
Since silicic acid is mainly present in hard water, mixing with osmosis water is also suitable. If sludge is introduced into a new tank from a run-in aquarium, the running-in of the new tank will accelerate.
As a result, the silicic acid converts more quickly and the diatoms lack this vital nutrient.
Osmosis water is also the appropriate measure if diatoms occur in the established aquarium. Lowering the pH value can also lead to the death of the diatoms. Of course, the demands of the aquarium inhabitants on the water hardness and the pH value must be taken into account.
Reduce phosphate content
The phosphate content in the aquarium water should not exceed 0.25 mg per liter of water. Otherwise, algae usually appear.
If the phosphate content in tap water is already too high, you should consider purchasing an osmosis system. In addition to other substances, this also removes phosphate from the water. If the tap water is not contaminated with phosphate, it must be checked how the excessive phosphate content in the aquarium water comes about. First and foremost, the suspicion lies in overfeeding or in the case of a high stocking of fish with correspondingly strong feeding.
Alternatively, an ivy can be planted with its roots protruding into the aquarium. Since ivy consumes a lot of nitrate and phosphate, they deprive the algae of their food base.
If, despite all measures, the phosphate content remains too high, the manufacturer of aquarium accessories can usually only use appropriate agents to bind phosphate from the water.
It may take a few weeks for these measures to be successful, since algae can store a certain amount of phosphate for later consumption. Only when these reserves are used up and no further supplies are available do the algae die.
increase illuminance
Since diatoms are more common in poor lighting, the illuminance can also be increased as an accompanying measure. However, if the excess of nutrients remains, other types of algae will certainly benefit and spread instead of the diatoms.
Presumably, diatoms do not prefer the dark at all, but grow with any lighting. Since other algae species generally don’t like low lighting that much, diatoms are probably more common in low lighting only because competition from other algae species isn’t as great.
Removal of diatoms
Diatoms can usually be easily wiped off plants and objects.
The algae are sucked off the substrate with a hose or the affected layers are washed out. They are removed from the pane with the normal tools for cleaning the pane.