How Can I Reduce the Algae Growth in a Saltwater Aquarium?

Every aquarium will eventually have an algae problem. Marine aquariums need special care when treating this problem because corals and invertebrates need calcium in the water. There are also fewer algae-eating species that you can add to your marine aquarium safely. Many saltwater janitors won't stop at eating algae in the detritus on the bottom of the tank, but may target other members of your cleanup crew like snails, slugs and shrimp or even your coral rock as food sources.

Things You'll Need

  • Low-nitrate sea salt
  • RO or DI water
  • Cleanup crew fish and invertebrates
  • Mangrove, macro algae and other saltwater plants
  • UV light sanitizer
  • Powerheads
  • Gravel siphon
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Instructions

  1. Reduce the Nitrates in Your Tank

    • 1

      Do less frequent but larger water changes. Use RO (reverse osmosis) or DI (deionized) water in the tank as some nitrates, as well as phosphates (another algae feeding nutrient), may be coming from your tap water. When you do the water changes, use a gravel siphon to clean the debris out of the gravel.

    • 2

      Check the nitrates in the sea salt mixture you are using. Some brands of sea salt have higher mixtures of nitrates than others.

    • 3

      Use mangroves or other macro algae plants in the sump pump or the aquarium itself to remove nitrates and other excess minerals in the water. This will control the algae growth and help clean the water of proteins. Added illumination will help your desired plants to outperform algae.

    Add Algae Predators

    • 4

      Keep trochus snails and sea hare slugs in your tank. These mollusks are very good at keeping surfaces clean of diatoms and algae. You can have one per every 5 gallons in your aquarium, according to Quality Marine. There are many other snails that will help keep the aquarium clean although this one is known for being less susceptible to being eaten by predatory fish that may share its tank.

    • 5

      Include hermit crabs -- Clibanarius digueti are often recommended -- in your cleanup crew. Some hermit crabs are known to eat the snails that you want to also keep your aquarium clean, but Clibanarius digueti are not known to eat snails.

    • 6

      Add lawnmower blenny, (Blenniidae family) and tangs (Acanthuridae family) to the tank. Both love to eat algae and are visually interesting. Blenny skip across the bottom of the tank while tangs are very colorful.

    Adjust Lights, Motion and Food

    • 7

      Reduce the amount of light that reaches your tank, especially sunlight. Tank lighting should be on no more than 6 to 10 hours per day. This will help to reduce the algae growth. Use specially manufactured bulbs that radiate in wavelengths that are preferred by corals and saltwater plants. Algae are better at absorbing other wavelengths of light, which the manufactures try to eliminate from these bulbs' light spectrum.

    • 8

      Avoid overfeeding the fish or the coral. Excess feeding causes protein skimmers to work harder and adds excess nutrients to the water, which algae will take advantage of.

    • 9

      Increase the motion of your tank water by adding powerheads and canister filters. Algae are easily displaced in areas of rapid water movement.

    • 10

      Add a UV sterilizer light to your tank filtration system. UV light destroys single-celled algae that can make your water green. Diatoms are also destroyed by UV light, which will prevent brown algae from growing on the side of the tank.