Good article part 1
Albert Thiel
Nutrient Control and Algae Control in the Marine Aquarium
August 9th, 1998
Algae becomes a problem whenever they take away from the "look" of the tank or, stated differently, from its aesthetic and visual appeal. When too many algae are present (both micro and macro) they may interfere with the growth of organisms because they will grow over and on them, thus "choking the coral or the animal. This is probalbly a far greater problem that the former. Looks is one thing, but loosing animals is another one entirely.
Note that all forms of algae can lead to such a situation, not just the so-called micro and filamentatious ones. Macro algae that overtake the aquarium will lead to the same consequences. In some cases even coralline algae can cause a problem if they lower calcium levels too much and make it unavailable or too low for corals.
There really is no simple pathway, or approach, for controlling excess algae because a number of factors are involved. Excessive levels of nutrient are in just about all cases the norm though, when algae growth gets out of control.
Nitrate, phosphate, silicate, carbon dioxide and dissolved organic matter are most often the cause of such growth. On the coral reef they are very low in concentration, often near zero and in the ppb range. In the aquarium they typically build up over time and thus accumulate, and become the basis for the appearance of filamenentatious, encrusting, and free floating algae and diatoms as well as macro algae.
Controlling these levels by direct and indirect action is the key to eliminating this "problem". Direct methods would include controlling the concentrations by various approaches directly, and indirectly by for instance reducing feeding (a source of nutrients), maintaining low population levels and so on.
More often than not though, bioload is something most hobbyists do not deal with as they keep adding animals to the tank. Dealing with the sources of nutrients directly is therefore a better approach in my opinion.
Let us quickly review some of the most important ones that we can use to do so effectively. Feel free to ask questions about the various methods and suggestions given here.
Using a Protein Skimmer: Foam fractionation is used to reduce Dissolved Organic Carbon or dissolved organics (DOC). Use an efficient model and make sure that the foam is dry and colored and smelly. Lowering dissolved organic material will in just about all cases eliminate problems with red algae and will lower the CO2 in the system as well (and as with all plants and algae CO2 is a major nutrient). Skimming eliminates matter from the tank before it can mineralize and increase the nutrient levels. This is a step higher up in the sequence of events than say, eliminating the nutrient directly (e.g. PO4) and is therefore a very efficient way to control nutrient levels by doing so before they occur.
Phosphates: Reducing and lowering PO4 is the one single most effective way of controlling most of the algae we do not want. Phosphate is found everywhere in nature. Nutrient import paths include ( nutrient get in the aquarium) from a multitude of sources: food, salt, carbon that leaches it, additives, and the raw water you use. R.O, D.I. and otherwise purified water such as well, or spring water will make a large difference in the concentrations of PO4 found in the tank. Phosphate levels should be at as low a concentration as possible. Recommended levels are in the 0.03 to 0.04 ppm. That is very low. Use any means you can to avoid adding PO4 to the tank from sources you can eliminate e.g. the ones mentioned above.