There are two types of true green algae that are commonly referred to as hair algae and are considered a nuisance in the home aquarium. They are Bryopsis plumosa and Derbesa (sometimes confused with the cyanobacteria: Lyngbya). Both can become major pests in the home aquarium of left unchecked in a nutrient-rich environment.
These algae have two distinct life cycles, the first being small bubble-like growths that are found attached to rockwork or substrate. Upon reaching maturity, these bubbles rupture and release spores, which eventually settle and grow into gametophytes. These gametophytes or "seeds" release cells that have the potential to ultimately become new hair algae growth.
Limiting hair algae growth doesn't have to be an endless battle. By controlling excessive nutrients and other contributing factors, we can extremely limit its growth to the point of it being virtually non-existent in our systems.
Excessive nutrients, which lead to uncontrolled growth, enter the system through various methods which include:
Water Source - Tap water can contain high levels of nitrate, ammonia, phosphates and other elements that contribute to hair algae growth. Many of these elements are added to tap water intentionally as rust preventives or for other reasons beneficial for human consumption. Many hobbyists fail to realize this and unfortunately, this alone can be a major source of nutrients that cause excessive hair algae growth.
Some aquarists purchase water through their local grocery store believing that storefront water filtering machines will provide reef-ideal water. However, these machines are more often than not poorly maintained and are not much better of a source than aquarium water from tap.
To ensure that these elements are not introduced to our systems through makeup water, we should either purchase a reliable reverse osmosis or DI filtration device or purchase RO/DI water directly through a reliable fish store. The initial costs of such a unit may be a little expensive, but it will quickly pay for itself in the money it saves as compared to other options.
Many aquarists will argue that their local water is safe and has never been a problem in the past. Unfortunately, local water sources are far from homogeneous. At times your local water authority may purchase water from an outside source which may result in high level of nutrients. Other times, foreign chemicals are treatments may be added to address problems. These things happen so tap water users beware!
Salt mix - Many low-quality salt mixes still exist on the market. Some of these contain impurities that contribute to hair algae growth. Talk to other hobbyists and your local fish store to find a good salt mix. There are many available that are of a high-grade that will do the job. If you like, you can contact me directly for my personal preferences. There are several that I find work well in the captive reef environment.
Feeding & Supplements - Both heavy feedings as well as many foods commonly sold greatly attribute to hair algae growth. Liquid invertebrate foods deserve mention here. They are more often than not unnecessary and add large amounts of dissolved nutrients to our systems. As far as heavy feedings are concerned, definitely don't starve your fish but certainly carefully feed and remove any uneaten foods.
Filter Media - Some granulated carbon as well as other filter media contain high levels of phosphate. Ensure all filtering media is labeled "phosphate free". Also, the use of plastic bio-balls or other bacteria colonizing media should be avoided. These types of media convert nitrite to nitrate far to fast for it to be safely removed from the system. It is best to let the natural processes in the sand bed and live rock handle these processes instead.
Poor Environment - Poor conditions also contribute to algae growth. Some commonly problems include:
Overcrowding & Detritus Accumulation - Systems with heavy bio-loads (too many organisms) directly increase dissolved organic substances in the water column. This is especially a problem for newer systems that are not yet fully established.
Additionally, fish waste that has accumulated at corners and around edges of rockwork should be siphoned out before it has had a chance to decompose and enter the water column.
Aeration & Water Current - Dead spots or areas of extremely low water flow are havens for unwanted algae growth. This allows a resting-place for nutrients to accumulate which may feed algae growth. Ensure that all areas in the system receive adequate current to carry away organics. When performing maintenance, use a small powerhead or wave of the hand to blow off any detritus that may have accumulated in tight spots.
Poor Lighting - While not a direct cause of algae growth, poor lighting can contribute to unwanted algae growth. Ensure that all bulbs are replaced as recommended by manufacturer. Also, when utilizing metal halide lamps, stick with 5K or better bulbs. Another aspect worth mentioning is the utilization of mercury vapor, halogen or other low-end bulbs. These bulbs are not the correct spectrum required by marine invertebrates and may actually encourage algae growth. If a green football field is what you are attempting to recreate, then by all means go ahead and use them. Otherwise, stick with bulbs made for marine reef systems are at a bare minimum, bulbs labeled "full spectrum".
Lack of Water Changes - Seawater has a tendency to degrade over time. Perform frequent water changes on a regular basis. For several hair algae outbreaks, this is very important. If you are using natural seawater, it is possible that this is the cause of your problem. Ensure that the seawater you are using isn't contaminated with heavy levels of nutrients.
Declining Sand Bed - A declining or failing sand bed may be saturated with organics. This is commonly not a problem if sand bed/plenum are properly setup and maintained with the exception of heavily stocked systems. Also crushed coral or gravel type substrates should not be used in reef aquariums. These substrates quickly trap detritus resulting in an almost guaranteed decline of overall conditions.
Methods of Control
Our first step is to limit all contribution factors as much as possible. Once this has been done, there are several things that can be done to help combat continued growth. Some of these are:
The Addition of Macro Algae - Higher algae can easily out-complete with nuisance algae for nutrients. Caulerpa is among the most beneficial macro-algae due to its prolific growth rates and high consumption of nutrients. It is important to keep this algae cut back so it does not overgrow the system. Also, large growth rates without pruning can lead to crashing of this algae. Something to keep in mind, this algae and many others can attach itself to coral tissue and rock, which can irritate the coral so take care.
Herbivores - Utilizing algal grazers (though to a limited extent) can help control hair algae. Astrea snails, various crabs, some fish and even urchins will eagerly eat hair algae. Keep in mind that many hobbyists are quick to over-do-it, adding too many herbivores that only add to the problem.
Maintaining a Healthy Sand-Bed – A healthy and properly established sand bed provides a heavy amount of micro-fauna, which play a direct role in algal control. These organisms are normally quite prolific and eat ditritus and other organics in the sand-bed before they have the opportunity to disolve and enter the water column.
Skimming - This may be the single-most important method to control excessive nutrients in a reef aquarium. Other than knowledge, a good skimmer is the cornerstone (in my opinion) to the successful husbandry of any marine aquarium. If you don't have a good skimmer, get one!
Competing Organisms – Tridacnid clams remove ammonia and nitrate from the system water though this could quickly get very expensive (they are far from inexpensive!). However, the addition of additional corals and other organisms that compete for nutrients also help to control algae growth. A reef aquarium with very few coral and other photosynthetic organisms is far more likely to be overrun with nuisance algae due to excessive nutrients being available, as well as a large amount of surface area exposed to direct light. A system heavy stocked with photosynthetic organisms easily out-compete lower algae for nutrients. Additionally, coral growth shades areas that would otherwise provide a good spot for algae growth.
Julian Sprung recently pointed out in his book, Algae, a problem solver’s guide that corals produce anti-fouling substances that inhibit or limit algae growth on and around them.
Chemical Warfare – The use of the various algae control agents currently on the market normally cause more harm then good. When they do work, they quickly kill algae growth (oftentimes desired species as well) and release heavy nutrients into the water column. DO NOT rely on these chemicals. Even if they do succeed in eliminating an outbreak, this is only a temporary solution. Eliminating the causing factors is the KEY to dealing with algae outbreaks.
There are also various types of phosphate absorbing media available and while these may assist the aquarist in controlling algae growth, once again they are not the solution.
Julian Sprung also mentions in his book (mentioned previously and highly recommended) that Ferric Hydroxide granules can be used safely in aquariums to control phosphate levels though I do not have any experience with this what so ever.
Closing
Be patient. Hair algae will not go away over night. Remove as much as you can as often as you can with your fingers, forceps, tweezers or any other way you can come up with. Then apply what I have outlined here. Find your source of excessive nutrients and eliminated it.
Remember, Don't waste your time on algae killers or other hemicals as these will only provide a temporary result (if any at all).
Additionally, it must be kept in mind that new aquariums more often than not will experience significant algae growth in the first few months of operation. This is normal and should be expected. In a probably setup system that is allowed the adequate time to become established without including too large of a biomass, these blooms will subside.
