AQUARIUM ALGAE
• Brown Diatom Algae
• Common Green Algae (aka Dust algae)
• Thread/Hair Algae
• Marine Hair Algae (green filamentous algae)
• BBA/Black Brush Algae/Black Beard Algae/Red Algae
• Cyanobacteria (Blue Green Algae)
• Summary

This Aquarium Answers article (post) is not intended as a complete algae control article, but is intended to address the types of algae that I receive the most questions about which are Brown Diatom Algae, Black Beard Brush Algae (BBA), and Marine Hair Algae aka Filamentous marine algae (I address other algae as well in this article). I will add to and update this article as well over time.

Updated 7/17/08

Brown/Diatom Algae

Brown Algae is not considered a true algae as per many biologists, rather a diatom. However under the 5 Kingdom classification system both Brown Diatoms and more common algae fall into the "grab bag" Kingdom; "Proctotista", although Brown Diatom Algae fall into the division Bacillariophyceae.

Diatoms also single-cell organisms but are significantly larger and more complicated than cyanobacteria. They have cell walls containing silica. The individual cells are yellow-green to brown. They contain two types of chlorophyll and at some stage in their life cycles have motile stages which move by the action of one or two tiny beating hairs called flagella.

Most diatoms show very limited mobility and exist primarily as groups of cells growing a film over the surface of objects. In low concentrations they probably don't have any noticeable effect in aquarium systems, and indeed they are probably always present.
These diatom cells are encased within a unique cell wall made of silica (hydrated silicon dioxide). The yellowish-brown chloroplasts within Brown Diatom algae are what give this “algae” its typical appearance.
Brown Diatoms are found in fresh and saltwater as well as soil. Diatoms are a major component of plankton, free-floating microorganisms of marine or freshwater environments. Not all diatoms float freely though; many may cling to surfaces such as aquatic plants, gravel, décor, molluscs, and crustaceans. Brown Diatom Algae are dependent upon silicates and high DOC (dissolved organic compounds) in the water and thrive in conditions where the minerals and Redox are out of balance. Brown diatom algae also out compete more desirable green algae in these conditions when light is poor for healthy photosynthesis due to lack adequate amounts of light in the proper PAR.

With the above points in mind, I will again emphasize that Brown Diatoms MUST have silicates present to reproduce, although removal of al silicates is often not feasible, in many of the methods (outlined in the removal tips below) the aquarist can lower the available silicates including by simply adding plants or encouraging green algae to grow which will out compete the Brown diatoms.
From the Aquarium Answers article; “Aquarium Test Kits” here are some silicate parameters: Natural seawaters contain silicates around 10 ppm however due to differences in a closed system (which an aquarium is) and the ocean it is best to maintain silicates under 1 ppm in an aquarium to prevent diatom blooms and aid in uptake of essential elements such as Strontium by corals.
In freshwater, silicates are generally between 4-20 ppm and should be kept under 4 ppm in an aquarium, although usually this is not a problem in healthy established freshwater aquariums where lighting is good to encourage plants or green algae (both of which will starve also consume silicates limiting diatom growth)

This is a common algae in new aquariums, especially aquariums that have not fully cycled as this leaves many available nutrients for these diatoms.
If an established aquarium struggles with these diatoms, this is often an indicator of excessive silica, poor mineral/electrolyte balance, an unstable biological aquarium environment (often caused by poor filtration, poor cleaning procedures, Redox Balance, Aquarium Lightingor over medication).

Here are a few tips (suggestions) for eradication of Brown Diatom Algae:

*Use re-mineralized RO water if silicates are high in tap water.
For saltwater 100% RO or DI water use is fine for both mixing with marine salt mix or topping off for evaporation. HOWEVER in freshwater I do not generally recommend 100% use of RO or DI water, rather blended water and even then it is best to re-mineralize with products such as Wonder Shells, and check the KH and adjust accordingly with products such as SeaChem Buffer or even SeaChem Cichlid salt which has other important minerals and KH enhancing carbonates as well.
*Correct proper mineralization with products such as Wonder Shells or other mineral blocks. Maintaining a correct KH, pH, and GH balance is a good place to start as well. The use of balanced buffers in marine tanks such as SeaChem Marine Buffer is highly suggested.
*Turning over gravel daily by hand and/or with a gravel vacuum slow the spread
*UV Sterilization also slow the spread of free floating diatoms and aids in the improvement of Redox Balance which is also important.
*A healthy, established nitrogen cycle is essential for control of Brown Diatoms.
*Correct lighting as per the amount in lumens and the correct PAR often usually found at about 6500 Kelvin (an incorrect PAR is often the problem when lighting is the reason behind Brown Diatom Algae growth in established aquariums). Generally around 9-12 hours per day is adequate. This will allow green algae and plants to out compete the Brown Diatoms. Please see this article for more information: “Aquarium Lighting, how it works”
*Live plants to “out compete” diatoms
*Cut back on feeding or switch to higher quality foods that is less likely to produce high amounts of wastes and may also be high in silicates.
*Use near boiling water on décor, rocks (not gravel), plastic plants, etc. This is VERY effective in killing brown diatoms while at the same time allowing the establishment of healthy green algae that will often survive this procedure. I have used this method for years with excellent results.
*Addition of salt (sodium chloride), this can aid in the control of many algae (not just Brown Diatom), however too much salt can interfere with your live plants (if you have them in the first place). I would recommend starting low, especially if live plants are present at 1 tablespoon per 5 gallons and then slowly increasing if needed.
*Oto Catfish or Otocinclus affinis are excellent fish that will remove and keep this algae in check in a planted tank.
*Snails, especially Nerite Snails (for FW OR SW). Please see the section on snails for further links/information in this article: "Aquarium Plants"
*Patience and time (about 8-12 weeks) for new tanks, often this is all it takes for a new tank.
*Please note that the suggestions using boiling water, algae eaters, and snails are methods to bring Brown Diatoms under control, however after the being "patient" with a new tank for a few months or in the case of established aquariums, these suggestions are meant for control and if their continued use is still needed this indicates other issues that need to be addressed such as organic load (DOC), lighting, mineralization, Redox, etc.



Common Green Algae (Sometimes referred to as Dust Algae)

This is the most common algae in established freshwater aquariums with or without plants.
This is the algae that coats the front and side glass. It's generally a good sign if that is the only algae that is noticeable in your tank. Generally simply scraping the glass and rinsing off plastic plants with a 1/25 bleach/water solution (followed by a rinsing with de-chlorinators and water) prior to your water change is all that's needed to control this easy to control.

Green Spot Algae

These are hard circular algae spots that take hard scrubbing too remove from the tank glass. Moderate to high phosphate limited tanks have more problems with green spot algae on plants. Green Spot Algae is often eliminated with increasing phosphate levels in your water. Try to maintain at least 0.3 to 0.5 of phosphates throughout the week and more preferable is in the range of 1.0 - 2.0 ppm of phosphates.
Some Plecostomus such as the Rubbernose may help, however these fish may also damage plants as well/


Thread/Hair Algae

Most Thread/Hair algaes grow extremely fast. You can manually remove handfuls every couple of days. After eliminating this type of algae is it a good idea to add an algae eating crew.
There are may fish that may help with this; Rosy Barbs, American-Flag Fish, Amano Shrimp, Bristlenose Plecostomus, even Platties.

Marine Hair Algae (green filamentous algae)

Although not the problem or scourge that red slime (Cyanobacteria), this algae can over take an aquarium in short order and is an indicator of high nitrates and phosphates. Although I consider algae growth generally an indicator of a healthy marine aquarium, normally I recommend less problematic algae such as the Macro-Algae. Macro-algae is the 'plant' and encrusting algae that you see in many experience saltwater aquarists marine tanks. Macro algae cut down on light available to the micro algae, and compete directly for the nutrients otherwise available to problem algae. Caulerpa spp, encrusting corallines (a group of Red algae resembling corals), Bubble Algae aka; Valonia macroalgae (although bubble algae can become problem algae on occasion as well) are examples here. Other beneficial algae that do not take over an aquarium include Green Gracillaria algae as these green algae are beneficial for nitrate reduction without the “overbearing problems of Green Filamentous algae which tends to take over an aquarium, often squeezing out your polyps, mushrooms, etc.

For Filamentous marine algae (hair algae), I would recommend changing water with marine salt mixed with RO water only.
I would also try and get a deep sand bed going in your aquarium or a separate tank for nitrate removal.
Finally I would suggest a clean up crew of creatures such as Trochus, Nerite, and Turbo Snails

I have information/links for deep sand beds and other methods for nitrate removal in my Marine Aquarium article: “Saltwater Aquarium Basics; Fish, Nano Reef, Reef” as well as this Aquarium Answers article about Nitrates: “Aquarium Nitrates”


BBA/Black Brush Algae/Black Beard Algae/Red Algae

Technically this is a kind of red algae, but that classification does not define its appearance. This unwanted algae often shows up on older parts of plants and on slower-growing plants. Black beard algae is a form of "red algae" in the genus Audouinella that commonly attaches to edges of plant leaves or drift wood and is more common in low CO2 water conditions, that are low in most minerals (although often high in iron), carbonates, and pH (although these algae will also grow in alkaline, high pH waters as well).
(Click on the picture to the left for another view)

This is in my opinion is the most aggravating freshwater algae I know of and I have not found a magic bullet for this as of yet. I also have plant keeping friends in hobby and profession that also want to pull their hair out when it comes to this algae.

This furry, thread-like flora attaches to various aquarium surfaces including the edges of plant leaves, filter tubes and even gravel. It may have many colors (purple, gray-green, black) and resembles beard hair or fur. In the aquarium literature, this nuisance is often called beard or brush algae.
Most aquarists consider BBA to come in three forms; The long thread variety is called beard algae, the shorter thread type is called brush algae; and a third type is described as having very short threads and forms dark semi-round spots.

Physically removing rocks and wood that have these algae on it and then scrubbing it off will also give plants a better chance of utilizing nutrients and over coming these algae. The use of Sea Chem Flourish Excel has been shown to be effective for some in control of this algae. The reason behind this is that Flourish Excel is formula is Aldehydes based which are effected by oxidation which is another indicator of the importance of VERY regular but often small water changes (as much as 5-10% per day) to bring about a healthy Redox (among other methods of Redox control). This admittedly is only a theory at this point, however I have observed vastly better algae control (of all sorts of algae) in ponds where I achieved a healthy Redox via flow through water changes, mineralization and a PROPERLY installed UV Sterilizer.
I have also found (as in Brown Diatoms) that pouring near boiling water over decorations such as rocks or filter returns, etc that have BBA o them works well for killing this algae while allowing establishment of much less onerous green algae.

Siamese Algae Eaters (SAE) are very good at keeping these algae in check (providing that there is not more tasty green algae or left over fish food). Some other fish such as Platties and Rosy Barbs will occasionally snack on BBA as well.

Cyanobacteria (Blue Green Algae)

Blue/Green Algae which is more appropriately called Cyanobacteria is more closely related to bacteria than algae, however it is worth noting here since it can be a difficult problem in both fresh and saltwater. Cyanobacteria is more common in a tank that is not healthy or that has a high load of dissolved organics. Cyanobacteria has many species and forms and causes great angst among planted tank beginners and experienced hobbyist alike. Some forms of BGA grow slow and are very difficult to kill, other species grow very quickly and can overwhelm and "smother" all the plants in short order.
For my full discussion of Cyanobacteria, please see my separate article about it:
“Cyanobacteria (Red/Orange Slime, Blue Green Algae) in Aquariums”


SUMMARY

I will finally add that most true algae (not Cyanobacteria) compete with plants for the same nutrients and light, so battling algae is often very difficult, however from my experience with ponds in particular it is often a war than cannot be totally won but certainly can be checked by keeping nutrients away from algae (such as substrate nutrients) while providing them to plants and understanding that algae are more simple life forms than plants and have less complicated needs, so addressing the more complex needs of higher plants will allow them to out compete (sometimes this is as simple as removal of as much algae as possible to give the plants a foot hold, although this can also be a much more difficult task).

When it comes to algae control in a planted tank this is also noteworthy as even though added carbon (CO2) will often help plants out compete algae, thus retarding unwanted algae growth, if algae grows out of control as soon as added carbon is removed, there are likely other problems contributing to this including;

*Unusable/ unavailable nutrients (micronutrients and macronutrients). Here is a list of important nutrients (listed in recommended added solution, not ppm as stated earlier in the article):
Potassium (often available as Soluble Potash)- .37%, Iron- .32%, Sulfur- .27%, Sodium- .13%, Calcium- .14%, Magnesium- .11%, Nitrogen- .07%, Nitrogen- .07%, Available Phosphate- .01%, Boron- .009%, Cobalt- 0004%, Copper- .0001%, Zinc- .0007% Molybdenum- .0009%,.
Here are a few sources: Sea Chem Flourish, PMDD , Regular Wonder Shells, Jungle Plant Tabs . Not all these sources have all the required nutrients many can be mixed as you find your own success.
Much has been published lately about the addition of PO4 (phosphates) to control algae, however I believe this is only partially correct and based on some false assumptions; PO4 along with NO3 and Potassium are important Macronutrients that need to be in balance. I have found that simply changing water will (assuming proper mineralization of new water) will control algae by adding all these macronutrients.
What is happening is that algae are much better equipped than higher plants to compete in conditions of low nutrients, however the addition of these nutrients allows much better competition. Adding only PO4 does not bring these macronutrients into balance and even though many claim this solved their problem, they have not run a control group to see if this was only part of the equation.

*Poor substrate for healthy plant growth (only certain plants!). Make sure your substrate is rich in Iron (Fe). Iron is the most important trace element; your tank substrate should contain a reasonable amount of Iron. Liquid iron will, if over dosed, favor Hair algae. It can be added through tablet Iron rich fertilizers and through substrates like Azoo Plant Grower Bed , Laterite and Fluorite

*Important! - Poor lighting that does not allow plants to compete with algae. Although when more light is added more nutrients including CO2 are needed. I do not agree with the method of darkening a tank for a few days as plants often have higher light requirements than algae (in part due to their complexity), this only gives the algae more time to out compete plants!

*High or too low Nitrates. Nitrates should be above 15 ppm for plants, but not above 40 ppm as I have seen in many aquariums with excessive algae growth (although high nitrates is rarely a problem in tanks with healthy plant growth). Too low and plants will starve for this important macronutrient.

* Aquarium Cleaning Frequency. Often increasing the frequency (even twice or tree times per week) will improve conditions in the aquarium so as to allow plants to out compete algae. In part this improves the macronutrient balance as discussed above (as well as improvements in Redox and lowering DOC). I however do not recommend increasing the amount of water changed.

*Trim plants of dying, decaying, or algae covered leaves, even if this removes much of your plants. This is much like pruning in your garden. This forces plants to generate new and healthy leaves that will often do better at out competing algae.

*Dip your new plants or even established plants, although this will cause a temporary shock to established plants.
Here are a few methods;
• Bleach used in a 20 parts water to 1 part bleach for 2-3 minutes for delicate plants and 4-5 minutes for broad leaf plants; followed by a quick dip in sodium Thiosulfate or other de-chlorinator/ water mixture (Sodium Thiosulfate is found in many aquarium/pond de-chlorinators such as Start Right and I recommend that the dose used to neutralize the bleach be double to triple the normal suggested amount for tank use).
• Potassium Permanganate in a solution of water and enough Potassium Permanganate to turn you water pink for 20 minutes is also effective for many algae, diseases and usually snails, again followed by a sodium Thiosulfate or other de-chlorinator/ water mixture.
• Sea Chem Flourish Excel , this product can be used as a quick dip solution (about 30 seconds) for plants to kill algae. I recommend diluting with about 5 parts water with 1 part Flourish Excel.
Also the dosing of Flourish Excel in your aquarium can be effective for algae control as well. Flourish Excel contains a polymerized isomer of glutaraldehyde trademarked as polycycloglutaracetal by SeaChem and is the active ingredient in this product, which is a fertilizer for aquatic plants. It is claimed that it provides a bioavailable source of carbon for higher plants that is not available to algae. Though not marketed as such due to federal regulations, the algaecidal effect of glutaraldehyde kills most algae at concentrations of 0.5 - 5.0 ppm.


*Improper GH and KH levels (or mineralization, especially GH). Here is a quote:
“The release of carbonate converted from bicarbonate by plant life can cause pH to climb dramatically (above 9) during periods of rapid photosynthesis by dense phytoplankton (algal) blooms. This rise in pH can occur in low alkalinity water (20 to 50 mg/L) or in water with moderate to high bicarbonate alkalinity (75 to 200 mg/L) that has less than 25 mg/L hardness.”
Source:
Interactions of pH, Carbon Dioxide, Alkalinity and Hardness

*A poor Redox Potential which is often improved by better and more frequent water changes and proper mineralization such as Calcium, Magnesium and sodium as stated above. Also the addition of UV Sterilization



Further Reading/References:
http://www.thekrib.com/Plants/Algae/red-algae.html
http://www.ucmp.berkeley.edu/chromista/bacillariophyta.html
Planted Aquarium Keeping Information
A Discussion of Algae
Algae; where they fit into the 5-Kingdom System