The algae growth I am seeing in my 20 gallon wide aquarium is referred to as Brush Algae. It forms small 3 mm dark tufts on plant leaves and equipment. This feather-like algae can come in different colors such as the black seen in my tank, and also purple, gray and greenish-gray.
If the literature I found on the topic is correct, this is a type of red algae. Knowing this can help if you are looking for a chemical treatment. There is a variety that produces longer strands and is commonly called Beard Algae. There is also some referred to as Hair Algae, but mine looks more like what is described as brush; small feathery round tufts of short, fine black hairs.
I have no particular idea where the algae originated from. It may have been transported from fish added to the tank, or from store-purchased plants or even from plants exchanged with other hobbyists. It may be that the algae was present in the soil source used for substrate. It's an unlikely cause because store-purchased potting soils are sometimes sterilized. Alas, I have no idea how the algae gets into aquariums. It just does.
So unless you relish this aquarium inhabitant, the challenge is to prevent its growth, keep it under control or eliminate it altogether once it's established.
As far as I can read, algae takes nutrients from the water. Plants may take up nutrients from both the substrate and the water. So in theory, plants have an advantage. Some plants feed heavily from the bottom, while others seem to hardly make any underground roots.
My current experiment is to starve the algae by reducing the amount of available chelated iron in the water. I am doing this by altering my liquid fertilizer solution in measures described in a previous post. I am also going to increase the duration of the light period because more light hours will increase plant growth. Plants compete with the algae for nutrients. If the plants are growing faster and better, I make the assumption that the algae will have less of a foothold.
If this current try-out does not help the situation within a month or so, I will try a last resort method: Copper. There are no crustaceans in my aquarium and the plants I maintain will probably not suffer from a strong dose of copper sulphate. We'll see.
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