The brown are Diatoms. It is a part of the cycling process. They are from the silicates in the water. As the silicates get used up it will slack off disappearing with time. If it get too out of control you could get algae eating creatures to help. They wouldn't mind a bit!
Examples would be snails, reef hermits and algae eating fish. The following came from this link..http://saltaquarium.about.com/librar...=Brown+Diatoms
Anyone who has ever had a saltwater aquarium at one time or another has probably experienced brown algae. Brown algae is actually not an algae at all, but a diatom. Brown algae outbreaks usually occur when a tank has just finished cycling. It can appear as a simple dusting on the tank surfaces, or it can turn into a massive growth that chokes everything in the tank. What you are actually seeing in your tank is diatom skeletons, all linked together.
Also referred to as microalgae, brown diatom algae is a precursor to green algaes, both in undesirable forms like green hair algae, and desirable forms like Caulerpa (macroalgae), that almost all aquarists try to cultivate. In other words, brown diatoms are one of the first to appear when the tank conditions are right for algae growth, which opens the door to other forms of algae.
In order to grow, all algae require only two things: light and nutrients.
The light in an aquarium comes from either sunlight or artificial lighting. Improper, poor, or extended lighting hours stimulates algae growth.
The nutrients algae normally need to grow are nitrates (NO3
). This is their basic "food".
Other nutrient sources (think of them as vitamins) are silicates and phosphates. Brown ditaom algae thrives on silicates, where green hair and other algaes prefer phosphates.
Low water flow (current) in a tank can contribute to slime and filamentous brown types of algae to grow in abundance. Low water flow produces high carbon dioxide levels, which algaes consume as well.
Nitrates are the end product of the nitrification, or the biolobical/nitrogen cycling process, which turns ammonia (generated from excess food and fish or invert detritus) into nitrites, and then into nitrates. So, the less nitrates in your tank, the less food for brown algae to grow on. Tanks which contain a high level of DOC
's (Dissolved Organic Compounds), which forms that "film" on the surface of the aquarium water, are great candidates for a brown algae outbreak. How do you get rid of the DOC
's? Either have a biological filter that will handle the load your tank is putting out, or use a good skimmer. A lot of people who have a terrific brown algae growth in their tank will say, "but my nitrate tests results are near zero!" Remember that big fat kid back in high school? How often did you see an uneaten Twinkie within 20 feet of him? Never. He ate every Twinkie in sight, just like the algae eats all the nitrates in sight! If you were to scrape all the algae out of your tank you would see a rise in the nitrate levels.
Silicates are the nutrient preference of brown diatom algae. This can be supplied to the tank by means of unfiltered/unpurified tap water or using the wrong kind of sand. Using RO
make-up water and proper aragonite type sand or gravel will help to eliminate the introduction of unwanted silicates. However, do watch the phosphate levels as well. If unchecked and ignored this opens the door for other algaes to take hold, since phosphates are their nutrient preference.
Another way to minimize the growth of unwanted algae is by introducing certain herbivores to your tank such as Tangs or Surgeonfish, and reef janitors or scavengers. These animals can play an important role in reducing the amount of nitrate producing material in the tank.
The bottom line is, don't provide the food sources that any type of unwanted algaes need to grow. Execute a regular tank maintenance program, don't overfeed, use proper lighting, provide proper tank circulation, use RO
make up water, and keep the tank DOC
's in check! For more information on how to control algae, nitrates, silicates and phosphates, as well as learn more about aquarium maintenance routines and other important factors that pertain to water quality, refer to the Aquarium Care Index.
Stan & Debbie Hauter
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