Cotton Candy Algae
Cotton candy algae is considered to be a nuisance algae. There are many species of cotton candy algae, none of which you want to see in your reef tank. Cotton candy algae, depending on species, may look like a red or pink cotton puff ball or a red, branching structure. Left unchecked, it can cover your live rock, your glass, your power heads, and even your corals. It will even grow between the polyps of Xenia, green star polyps, and palys, making removal difficult. There are more than 400 described species of cotton candy algae, and all are red, and irregularly branching. Even different types of water flow can change how the alga grows, with stronger current producing stiffer branches.
Cotton candy algae is classified as a red algae and is in the genus Callithamnion, from Phylum Rhodophyta, Class Florideophyceae, Order Ceramiales, Family Callithamniaceae, and Tribe Callithamnieae. All red algae (Rhodophyta) never posses flagellate forms, unlike the other forms of algae. These obtain their red color due to their pigment phycoerythrin. Because phycoerythrin can be in different densities, red algae can be black, red, or even blue and green. These are more commonly found in warmer, tropical marine waters, but some species thrive in fresh or cooler waters as well. Almost all red algae are multicellular and will usually have a leafy or feathery form. The red algae Porphyra are used by the Japanese to wrap sushi. Coralline algae, typically lavender in color, commonly encrusts over live rock.
An algae bloom is a sure sign of a change in water quality. You may have an algae problem if you have too many nutrients in your aquarium, like phosphates or nitrates. You may be over feeding. Many aquarists make the mistake of "feeding" their corals, when many corals thrive without direct feeding. Often, corals rely on their zooxanthellae or the planktonic community for nutrients. If you are using food additives, you are basically adding waste to your aquarium. So, food additives can actually harm your water quality. Another mistake is not using RO/DI (reverse osmosis/de-ionization) water. Some hobbyists use tap water with a de-chlorinator for their water changes. Others may have an RO system, but do not change the resin and filters often enough.
Removing Cotton Candy Algae
The first thing you should do is pull the algae out by hand. Turn off your pump and power heads if you can. Removing algae in high flow increases the chance algae will just start growing in another area of the tank. If your fingers can reach a puff, grab it and take it out. The sooner you remove the algae, the better, as you can help stop it from spreading. Unfortunately, you won't be able to reach every crack in every rock. It is also recommended to do more (and more frequent) water changes until the water quality of your aquarium has improved. You should remove debris from your tank, as well. We recommend regularly siphoning the debris from the bottoms of display tanks and sumps, as well as blowing detritus from the rock.
A fun method of algae removal includes the introduction of invertebrates to "graze" on the nuisance cotton candy algae. By far, Mexican Turbo snails are the most widely used method to combat cotton candy algae growth. In fact, some hobbyists on the forums have reported returning their Mexican Turbo's to the local fish store because they run out of food so quickly after clearing the problem. Remember, if your snails die and rot in the tank, you just added more nutrients to the water for the algae to grow back. Mexican Turbo's do not live as well in tanks which are hotter than 78° F.
Some reef keepers don't like these snails, however, as they are prone to knock over items in the aquarium. Other options include sea urchins, and sea stars, and sea cucumbers, which help with algal mats. In fact, most echinoderms are helpful with algae removal in general, not just the cotton candy variety. Although this is supported by reports on many of the forums, we have not had the same success in our experiences.
Rabbit fish will eat the cotton candy algae, but they may also graze on your corals. One hobbyist endured losing her zoanthids to the fish once it ran out of algae to eat. Rabbit fish are not recommended as they will occasionally pick at your corals and will be too large for smaller aquariums. Others have tried lawnmower blennies with a little success. Tangs are common algae eaters, but they seem to prefer green algae, and ignore the red varieties.
Controlling Cotton Candy Algae from Returning
Now that you have gotten rid of the nuisance algae, you need to make sure it does not return. There are a few things you can do to control the water quality to avoid the issue in the future.
Ensure you have the proper circulation and current strength for your aquarium. These are not the same thing. You might have only one power head, and hence flow in only one direction. Salty Underground often has success with more than one pump or powerhead in an aquarium. Placement usually creates a swirling motion in the aquarium to prevent water stagnation in any point of the aquarium. By keeping detritus in the water column, it can be removed in the skimming process. If you see sediment collect in certain areas of the tank, either adjust your power heads or resign yourself to siphoning out the debris on a regular basis.
Another way to prevent nuisance algal growth is to have the proper filtration. This may range from the mechanical filters found in bio-balls, activated carbon, and skimmers to biological filtration. There are many methods for biological filtration. These include use of live rock, live sand, refugiums, and algal scrubbers. The most successful aquariums have a combination of many of these methods. We use phosphate reactors for most of our tanks and for many of our clients' tanks. Obviously, filtration will not take care of everything, so it is important that you keep on schedule with your water changes. You may need to increase the frequency of your water changes, increase the volume of your water changes, or more likely increase both.
You should also consider investing in a "clean-up crew". Invertebrates like hermit crabs, emerald crabs, and a whole variety of snails will take care of leftover food and other detritus. Remember that the fewer nutrients you have in the tank, the better.
Growing macro algae will also help prevent the growth of microalgae like the cotton candy algae. They will compete with the "bad" algae for space, light, and nutrients. Some aquarists keep their macro algae separated from their corals by either keeping them in their own aquarium (refugium) or by regularly trimming them in the main tank. For example, some hobbyists keep Cheatomorpha in their sumps, and remove portions of it as it grows into a large mass. Additionally, macro algae act as a bio-filter, improving the quality of water. They also provide a unique habitat for the micro fauna of the aquarium as well, in the form of amphipods and copepods.
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