Here are some of the most common types:
Thread algae: These algae form long, thread-like structures and can grow on plants and decorations in the aquarium. They can affect the appearance of the aquarium and should be dealt with quickly.
Brush algae: These algae have a bristle-like structure and can be green, brown or black. They can spread quickly and affect the appearance of the aquarium. 
Blue-green algae: This algae often forms a blue-green layer on objects in the aquarium. They can be poisonous and should be removed immediately.
Brown algae in the aquarium have a characteristic brownish color and an irregular, slightly matted texture. They can appear on the surfaces of decorations, plants and even the bottom of the aquarium. If left uncontrolled, they can spoil the appearance of the aquarium and hinder the growth of other plants.
Bearded algae in aquariums have a distinctive appearance with green or brown, thread-like structures that look like small beards. These algae can reach a length of up to several centimeters and can often be found on plants or decorations in the aquarium. Beard algae can also grow on the surfaces of rocks, glass or filters and can affect the appearance of the aquarium over time.
Spot algae in the aquarium have a characteristic round or oval shape and can occur singly or in groups. They are usually very small and can only be seen with a magnifying glass or microscope. Spot algae can be greenish-yellowish, brownish or even red, depending on the conditions in the aquarium. They can grow on plants, decorations and even on the glass of the aquarium. When present in large quantities, they can spoil the appearance of the aquarium and result in an unsightly green or brown coating.
Diatoms, also known as diatoms, have a distinctive siliceous shell that gives them a distinctive appearance. They can come in various shapes and sizes, including single-cell cells arranged in long chains or delicate structures. Under the microscope, you can often see a fine structure or grid pattern on the shell of diatoms, giving them a shiny, silvery or golden-brown color. In the aquarium, diatoms can be brown or green in color and usually adhere to objects such as rocks, plants or the aquarium glass. However, heavy growth of diatoms can cover the entire aquarium and result in an unsightly appearance.
