What Are the Brown Spots Growing in My Aquarium?

The discovery of brown spots on glass or rocks inside an aquarium is common to most fish owners. But this is no cause for panic. The brown spots on the inside of an aquarium are called brown algae or diatomic algae. Brown algae, if removed immediately will not contaminate the water or harm fish.

  1. Brown Algae

    • Brown diatom algae are among the most common types of phytoplankton, which are microscopic organisms. The algae are found in oceans, aquariums, freshwater or soil. Many first-time fish owners disregard the brown spots as a dirty film from fish food or waste and simply wipe it away. However, brown algae cannot be eliminated by simply wiping the spots away. Specific cleaning procedures and ongoing maintenance will lessen the chance of algae growth.

    Growth

    • Brown algae feed off of silicates. Silicates can come from the water used in the aquarium or some sands or rock used for decoration. Pet stores and most big-box stores sell silicate testing kits. High levels of iodine in aquarium water also contribute to growth. The prime time for algae to grow is during the cycling period. The cycling period within an aquarium begins when high levels of nitrogen oxide 2 and organic carbons are concentrated. Levels of nitrogen oxide 3 and 4 are low during this cycle. Algae also thrive in warm lighted tanks. You can turn off the lights for a few days at a time without harming the fish.

    Removal

    • The removal of brown algae is time consuming. If you notice brown spots on the glass or decorations, empty the tank and clean it out; specifically wiping away the algae areas. Use a clean brush when scrubbing a tank ,and avoid using sponges that trap germs. Test the aquarium water after the tank is refilled. If silicates are present, consider using a phosphate remover. Products come in drops or sponges and eliminate silicates as well as phosphates. Using water that has been through reverse osmosis also reduces silicates. Change the aquariums filter if you are concerned algae is present.

    Maintenance

    • Regularly change the water in your aquarium using silicate-free water. Change filters according to the manufacturer's directions. Although the aquarium lights are still glowing, lights over 6 months old create a different emission that promotes algae growth. Consider keeping algae-eating animals in your tank. Ramshorn snails, Otocinclus catfish or Mexican red leg hermit crabs are commonly kept in aquariums for algae relief. Some aquarium owners use macro-algae against brown algae. Caulerpa is coral-shaped algae that grow quickly. Caulerpa works by stealing essential nutrients the brown algae needs to survive.