If a brown coating covers the substrate of your aquarium and looks unattractive, let’s hope it is diatoms! The alternative would be smear algae - and they are not as easy to get rid of as diatoms.
Diatoms only look great under a microscope: They are among the most beautiful geometric forms in the plant kingdom. But without a microscope they are really ugly, although they do not disturb or negatively affect the fish at all. In the wild grazing cichlids of Lake Tanganyika and Lake Malawi even eat up a large percentage of the diatoms.
If there is a brownish coating in your aquarium, first quickly test whether they are really diatoms. Take a piece of the brownish coating between your fingers and rub it. If it feels rough, it will be diatoms. Smear algae always remain greasy when rubbed. Then use the JBL SiO2 Krzemian Test to test the silicic acid content of the tap water with which you have filled your aquarium. By the way, the terms silicic acid and silicates are used synonymously (i.e. they mean the same) and they are the cause of diatoms. The pretty algae shells visible under the microscope are made of silicate. If the silicate content is above 0.8 mg/l, they can form these shells and cover our aquarium with the brown coating described above.
To get a grip on diatoms, you only have to remove the building structure, the silicic acid (silicates). Put a bag of JBL SilicatEx rapid in your filter and the diatoms will recede and disappear completely after a short time. If the silicate test in your tap water shows a high silicate content, you really need to work permanently with a silicate remover in your filter. But as I said – smear algae would be much worse to deal with!