Controlling Algae in Your Saltwater Aquarium


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Are you having trouble with excessive amounts of red slime, blue-green, cyanobacteria (brown diatom), green hair, bubble or other type of algae growth in your aquarium? There are a number of factors to consider when trying to figure out why you are having an algae problem. The growth of any algae is based on the following factors:

  • The intensity and quality of light they are exposed to.
  • The amount of nutrients (DOC's - Dissolved Organic Compounds) they have to feed on.
  • The amount of nitrates and phosphates, and for diatoms, the silicates they have to feed on.
  • Using an improper make-up or top-off water source. (Tap water usually contains nitrates, phosphates and other unwanted elements).
  • Using a poor quality sea salt mix. (One that contains nitrates, phosphates or other unwanted elements).
  • Poor or inadequate aquarium maintenance care. (This allows excess amounts of nitrates, phosphates and other unwanted elements to accumulate).
  • Low water flow or circulation in the aquarium.
  • No natural algae eating predators.

The appearance and growth of algae in an aquarium is not bad, it's just the natural order of things. In fact, it shows that an aquarium is well balanced and healthy, and the cultivation of macro forms is actually beneficial. Only when the algae is allowed to grow out of control and cover everything in the tank is when it becomes a problem. The above contributing factors are what can allow algae to grow into nuisance proportions, and here are suggested standard methods that can help to reduce or control them:

  • Remove excess amounts by hand, siphoning or filtration.
  • Adjust the lighting higher or lower, depending on the type of algae you are dealing with.
  • Remove excess nutrients (DOC's) through protein skimming.
  • Reduce nitrates and phosphates.
  • Reduce silicates by using the proper substrate (gravel/sand/live sand) material. Aragonite types are best.
  • Use RO or DI water for make-up or top-off water.
  • Use a good quality sea salt mix. (Be careful when choosing carbon too, as this can introduce unwanted elements as well).
  • Increase or decrease the water flow or circulation in the aquarium, depending on the type of algae you are dealing with. For example, Cyanobacteria species like red slime algae prefer low current areas, while most hair/filamentous species prefer high current areas.
  • Add natural algae eating critters. Various forms of green, brown and red algae can provide browsing food for many types fish and inverts, and many macroalgae species are actually cultivated in the aquarium for this purpose. There are a lot of marine inhabitants that depend on algae as a major part of their diets. Tangs and Surgeonfishes of the Zebrasoma & Ctenochaetus species, and most Angelfishes are prime examples.
  • If your fish friends can't keep up with the algae growth, you can periodically harvest it to keep it in check without completely eradicating it from your system. Introducing additional herbivores like Snails and Hermit Crabs, as well as detritivores like Starfishes, Sea Cucumbers and Marine Worms are all greatly beneficial. Just be sure to get the correct types that will eat the kind of algae you are dealing with.
  • Grow some competitive macroalgae. In Robert Fenner's (author of The Conscientious Marine Aquarist) WetWebMedia Green Algae-The Chlorophyta article he discusses both good and pest types of macroalgae. Under the Benefits - Algae Control section he points out that by growing an initial batch of algae, this in turn can "limit" the growth of unwanted pests types like slime, hair, fungus and bacteria forms. Because all algae compete for the same light, nutrients and space that is available in an aquarium, the growth of a good type of competitive macroalgae deprives the pest types of these elements to grow aggressively.

    There are endless chemical additive products on the market for algae removal and control, but we feel that proper aquarium maintenance is the key! With good tank management, algae should not present a problem. The only time we see an algae "bloom" in our tank is when we have missed a few routine cleanings on the tank and filter. If you feel you need to use over the counter remedies, talk to a knowledgeable pet shop or mail order supplier that can recommend products to use, and use properly, we might add.

    Did You Know: Copper sulfate was originally used in ponds and tanks for algae control, and it was a secondary discovery that it also helped control parasites on fish. If you have ever treated a fish-only tank (no LR, corals or inverts) with copper, you may have noticed you didn't have an algae problem.