The Types of Mold Found in Fish Tanks

What most novice aquarium owners might think is mold growing in their fish tank is most likely one of several types of algae. Algae is a primitive form of plant life that occurs naturally in every aquarium. Aquariums can be infested with organisms called diatoms, which are microscopic animals that secrete a hard shell on which algae will grow. Aquariums can have a slimy growth called cyanobacteria, which grows much more rapidly than algae.

  1. Black Brush Algae

    • Also known as beard algae, black brush algae looks like small tufts of black hair that can be found forming on slow-growing plants like anubias and on gravel. This type of algae can be one of the most difficult types of algae to control. Remove the entire leaf of a plant that in infested, this algae cannot be cleaned off the leaves. Octinclus.com recommends adding siamensis, the only fish that eat this type of algae.

    Green Spot Algae

    • This type of algae grows in spots on tank glass or plant leaves. Remove plant leaves that are affected. To remove it from glass, use a razor blade or scrub pad designed for acrylic tanks. Most fish won't eat this type of algae because it is adhered to the glass.

    Staghorn Algae

    • Staghorn algae is slimy, blue-gray-green in color and branches out in thick strands. Staghorn algae usually grows in high-light areas of the tank where water movement is slow. It can be removed easily by hand. Remove leaves of plants where it is attached. Siamensis will eat this type of algae. Move your tank out of direct sunlight and lower light levels in the tank if this form of algae is a problem, Octinclus.com recommends.

    Green Thread Algae

    • This type of algae will grow quite quickly and can take over a tank in just a few days. It grows in long, wispy strands and can be removed by hand. To control it, you will need to adjust light levels in the tank and nutrients in the water. Most algae-eating fish will eat green thread algae, even shrimp.

    Green Water Algae

    • This is a single-cell algae that floats in the water, turning it a cloudy green. According to Octinclus.com, the only way to remove it is to use a diatom filter to control nutrients in the water. The only fish that eat this type of algae are water fleas and small fry.

    Blue Green Algae

    • Blue green algae is really not a form of algae but a type of bacteria that grows over gravel, under rocks and up the sides of the tank. It is recognizable by its musty odor and is usually the result of poor water quality. Improving the water condition, manually removing as much of the algae as possible and adding the water treatment Maracyn can aide in controlling blue green algae, Octinclus.com says. No fish will eat this type of algae.

    Cyanobacteria

    • Cyanobacteria is not actually algae and can be green, black, blue or red. A slimy growth, cyanobacteria thrives in well-lighted aquariums with high levels of phosphate in the water. It is easy to remove but difficult to control, according to Aquarium Pros.com. It grows much more quickly than algae and even after completely cleaning the tank will grow back in just a couple days. To reduce cyanobacteria, clean the tank thoroughly and dramatically reduce the light to the aquarium for several weeks. Aquarium Pros.com also recommends treating water with Boyd's Chemi Clean several times until the problem is under control.