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Saltwater Algae Types

Algae are simple, aquatic organisms that can be as small as a single cell, or as large as seaweed that grows to more than 200 feet. They contain chlorophyll that synthesizes chemical compounds when exposed to light. Algae are important because they are at the bottom of the food chain, providing both oxygen and food for other marine life. They are hardy, adapt to many different water conditions and reproduce easily. The algae found in saltwater aquariums do not need to be removed unless they grow out of control by using up too much oxygen when light is absent, covering other aquatic life, clogging the filters and ruining the view. Five basic types of algae are most likely to be found in saltwater aquariums.

Green Algae
- Green algae (chlorophyta) thrives in environments with abundant light and is the most recognizable type of algae found in saltwater aquariums. The two types of green algae most commonly encountered are hair algae with its long, wispy strands of green, and green dot algae, that looks like green dots on aquarium sides. Hair algae is easily removed from the tank, but the removal of green dot algae is time-consuming and difficult.
Brown Algae
- Brown algae (phaeophyceae) often appear within two weeks of starting a tank and thrive in low-light conditions. Brown algae in a more established tank indicates an imbalance of nitrate and phosphate in the water. The aquarium may need to be cleaned and the lighting increased.
Red Brush Algae
- Red brush algae (rhodophyta) grows in a mat or brush-like form. It is actually a shade of pink and thrives in water with a high pH, plenty of light, and in some cases, calcium. Red brush algae grow slowly and are rarely a problem in the saltwater aquarium.
Diatoms
- Diatoms (bacillariophyceae) have silica (glass) shells. They sometimes form a slimy, golden brown layer on aquarium sides and objects within the tank. Diatoms are not usually a problem, but can bloom and create cloudy water in new tanks or those that are badly maintained with poor water quality and low lighting.
Blue-Green Algae
- "Blue-green algae" (cyanobacteria) are not really algae and appear as a dense slime taking over the tank. They can also be red or black in color, and are dangerous for other aquatic plants and fish. Blue-green algae overgrowth indicates a tank with poor water quality and/or stagnant water.

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