Is There Something I Can Put in My Aquarium to Prevent Algae?

The key to preventing algae in a freshwater or saltwater aquarium is to remove what the algae needs from the water system. Some algae growth in the aquarium keeps the aquarium healthy because many animals, such as fish and beneficial micro crustaceans in saltwater aquariums, will eat it. What most aquarists try to avoid is an algae "bloom," or the sudden growth of nuisance algae that can easily take over the aquarium.

  1. Phosphates

    • Phosphates are one of two chemicals needed by algae to thrive. Phosphates are introduced to the aquarium through water changes and food. Unfiltered tap water often contains phosphates and it is therefore best to use filtered water for your aquarium. Flake, frozen, freeze-dried and other foods usually contain phosphates. This is harder to avoid adding to the aquarium since the fish need to eat. To help remove the phosphates from the water you can add products containing aluminum oxides and iron hydroxides that will bind with the phosphates and remove them from the water. Some aquarists do not recommend using products containing aluminum oxide because these will leach aluminum, a toxic heavy metal, into the aquarium water system.

    Nitrates

    • Fish excrete ammonia into the water as waste. The process by which bacteria convert ammonia to nitrite and then to nitrate is called the "nitrogen cycle." The end product of the cycle, nitrate, is a fertilizer for algae. Keeping nitrates low or undetectable is crucial in preventing an algae bloom. Changing 20 percent of the water every week with freshly prepared water will usually keep nitrates low. However, you can use nitrate sponges in the filtration system that will chemically extract nitrates. This is not a permanent solution, however, but it will work for lowering nitrates temporarily.

      Biological filtration methods provide a longer-lasting solution. For freshwater aquariums, a biological solution to remove nitrates is to add live plants. The plants will absorb the excess nitrates from the water, slowing down the growth of algae.

      For saltwater aquariums, macroalgae is a preferred biological method. Macroalgae looks and grows like a plant and is sometimes referred to as a marine plant, although it is technically a form of algae. Some examples of macroalgae are halimeda, kelp, maiden's hair and chaetomorpha. Plants and macroalgae will also help control phosphates.

    Chemical Algae Removers

    • There are products for both saltwater and freshwater aquariums that promise to kill algae, and some targeted to a specific type of algae such as blue-green algae. These generally are only short-term solutions to an algae bloom and will help you get the upper hand when battling a sudden growth of algae. Controlling the phosphates and nitrates will prevent algae growth and the chemical treatments should not be needed.

    Deep Sand Bed

    • If you have a saltwater aquarium, another method for helping reduce algae growth is to use a deep sand bed either in the aquarium or in a separate filtration system, such as a sump. Deep sand beds are simply 4- to 5-inch deep sand beds made from argonite sand. The depth creates an anoxic zone -- a zone of little oxygen -- and allows for nitrate-removing bacteria to grow.