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Algae - Saltwater

Fish Care

Basic steps to reducing algae:

  • Use purified water and chemical filtration to ensure phosphates are not present.

  • Test for phosphates and nitrates.

  • Ensure your salt mix doesn't have phosphates in it.

  • Use a protein skimmer.

  • Use Kalkwasser to keep the pH between 8.2 and 8.4, especially if you don't have live rock or live sand. Kalkwasser is a German word meaning "lime water" and it is basically calcium hydroxide. It is used to help maintain proper alkalinity by helping to restore proper pH levels as they naturally decrease in a tank over time. Kalkwasser also contains strontium and iodine, which replace trace elements which are absorbed by reef organisms. Kalkwasser does not contain nitrates or phosphates. Kalkwasser can be added whenever pure freshwater is added to top up an aquarium.

  • Ensure adequate oxygenation of the tank. Consider carbon filters.

  • Do regular water changes every couple of weeks, with more frequent changes when your fish populations are higher.

  • Vacuum the bottom of the tank every couple of weeks and refill the tank with properly mixed saltwater.

  • Reduce lighting to less than 12 hours per day.

  • Add fish and invertebrates that graze on algae, such as snails, hermit crabs, sea urchins, yellow tangs, blennies, rabbitfishes and angels.

Types of Algae:

  • Diatoms (Bacillariophyta) - floating brown algae that is among the first algae to appear in a tank.  These develop silica shells and are abundant in plankton. Ensure proper filtration, as they live on organic wastes.  Attempt to reduce silicates and increase marine organisms that will eat them.

  • Brown Algae (Phaeophyta) - among the first algae to appear, as a matted covering over the substrate. Caused by high nitrates and silicates. Remove any sand not obtained from the ocean. Use reverse osmosis water to ensure further silicates are not introduced.

  • Green Algae (Chlorophyta) - one of the most common forms of algae in fresh and saltwater.  Develops from chorophyll and nitrates.  Reduce lighting and nitrate levels.

  • Hair Algae (Spirogyra and Bryopsis) - These are specialized forms of Green Algae (Chlorophyta) with light green strands that grow rapidly and attach to any surface. They thrive in the presence of nitrates, so take steps to reduce levels.

  • Blue-Green Algae (Cyanobacteria) - starts in one location and spreads steadily. Caused by high nitrates, high lighting levels and organic material in the water.

  • Brown Slime Algae (Dinophyta) - This algae can propel itself through the water and then accumulate on surfaces. This algae is beneficial for corals, clams, anemones and sponges. It can be controlled by reducing nitrates and increasing corals and invertebrates.

  • Red Algae (Rhodophyta) - The is coralline algae. It is beneficial in a reef tank and thrives when Kalkwasser is used. Coralline algae helps reduce other less desirable forms of algae.

  • Green Water - Free floating single celled green algae that thrive under high lighting and nitrates. Reduce nitrate levels and lighting. Increase oxygen levels. Don-t bother with water changes, as these can actual enhance algal blooms.