Need help identifying the algae in your aquarium? See the descriptions of the main types of aquarium algae below. And remember, regardless of which type of algae grows in your aquarium, the most effective way to combat them is to keep nitrate levels to a minimum.

Filamentous algae

These algae are usually light green, but also occur in dark green to brownish green colours. They grow in filaments and can attach to almost any surface. The growth rate of these algae is very high.

Filamentous algae usually enter the aquarium together with plants, snails, fish, snags and others. The most common species are Cladophora (rough to the touch), Spyrogyra (slimy to the touch) and Pithophora (rough to the touch).

Brown algae

Brown algae, or diatoms, are unicellular, brownish coloured. It quickly turns brown and can cover the entire aquarium in as little as 5 days. Diatoms are restricted in standing water, but transfer rapidly to all corners of the aquarium in the current flow.

Dinophyte algae - dinoflagellates

Dinophytic algae are symbiotic algae that supply many marine invertebrates with nutrients. Corals, molluscs, anemones and sponges feed on them.

Dinoflagellates have two flagella that allow them to move through the water. When unchecked, dinoflagellates form a brown slimy film that covers most of the surface in both salt and fresh water.

Blue-green algae - cyanobacteria

Blue-green algae, which despite their name, take on a pinkish-red colour in the aquarium, due to which they are also called red slime.

Cyanobacteria are single-celled algae. These algae usually begin in one spot (dark, with little water current) and then spread rapidly throughout the aquarium. In an optimal environment for them, these algae can double every 20 minutes.

Green aquarium water

Green water is often called "pea soup". Free-floating single-celled algae (Euglena) grow so fast that the water turns green.

As with most algae, these single-celled planktonic algae are capable of photosynthesis. During periods of light, oxygen is produced during this process.

At night, the algae absorb oxygen from the aquarium, which may lead to unfortunate consequences for the fish. Strong aeration is therefore required in the case of greenish water aquariums.

Black beard

Audouinella, which is black or dark purple, mainly occurs on aquarium plants. It begins to grow on leaves and eventually invades new areas in the aquarium. Aquariums with soft water and high CO2 concentrations are the most susceptible.

Causes of algae

Certain types of algae have different requirements for their normal development. These requirements include light, nitrogen, phosphates, silicates, dissolved organic substances, bicarbonates, iron, CO2 as well as many trace elements and minerals. They are all interconnected and play a role in algae development. Algae spores are present in the water, and they will surely take hold and begin to grow as nature has programmed. Imagine enclosed parts of your backyard. Grass will grow first, then weeds will grow, followed by bushes and then trees. All of this is part of a natural succession.

Near-ideal water parameters do not mean that algae will not grow in such conditions. They will simply be in a suppressed state.

Remember that an aquarium does not only consist of the aquarium itself. Filters, hoses, filter inlets, filter outlets, decoration, corners, niches - all may collect debris, which in turn may become breeding grounds and a source of algae spores. Therefore, keep your aquarium clean and do not neglect weekly preventive measures.