Brown Discoloration on the Walls & Gravel in an Aquarium

All aquariums are potentially susceptible to algae problems. Dormant spores and diatom organisms occur naturally in the water, waiting for the right conditions to develop into a brown fluffy residue inside your fish tank. Brown discoloration is particularly common in new tanks where the filter is not mature. Surplus nutrients from excessive feeding kick-start the diatoms, encouraging them to multiply, coating aquarium glass, gravel and decorations with a layer of brown slime.

  1. Causes

    • Most types of algae flourish in bright light, but brown algae is a symptom of not enough light in your aquarium. Brown discoloration on gravel occurs when there is not enough light reaching the bottom of your aquarium. A lack of light combined with decomposing fish waste provides the perfect recipe for diatoms to grow and take over your tank. Chemicals in domestic tap water such as silicates also encourage brown algae to flourish.

    Treatment

    • Wipe away the brown discoloration using a clean cloth. Start with clean glass and siphoned gravel so you can monitor treatment and algae development accurately. Establish the correct lighting levels for your aquarium. Tank size, fish stock and temperature all play a part in how your tank runs and how quickly algae develops. Leave your tank lights switched on for 10 hours each day and off for 14 hours. If brown algae continues to appear, keep the lights on for 11 hours a day the following week. Increase light levels in hourly increments until the diatoms stop growing. If green algae appears, there is too much light so reduce the light by half an hour each day until you reach your tank's optimum lighting levels. Change a third of the water every week to reduce the number of spores in your tank.

    Prevention in a New Tank

    • A new aquarium needs time to stabilize biologically, and the first four months are when water quality problems arise if left unchecked. Always use a water dechlorinator solution to remove chemical deposits in tap water during a water change. Monitor pH levels and check your aquarium for ammonia, nitrate and nitrite using aquarium water testing kits. Siphon gravel to reduce the amount of waste and do not overfeed your fish. Establish the correct lighting needs of your aquarium to prevent brown and green algae growth.

    Prevention in an Established Tank

    • Mature water in an established aquarium should be stable and toxin-free if the tank is correctly maintained, but dirty water or poor maintenance can cause brown algae problems. A partial water change is a quick fix for minor water instabilities or chemical fluctuations and 15 to 20 percent changes every two weeks are beneficial to the long-term health and stability of aquarium water. Uneaten fish food and feces provide a breeding ground for bacteria, so keep organic waste under control. Use a fine fish net to remove debris on the gravel's surface before it starts to decompose and siphon to the bottom of the aquarium gravel once a week.