Cyanobacteria - What is it and how can I get rid of it?

If you do a brief search in Google¹ or Wikipedia², you’ll get the general overview of this photosynthetic algae-like bacteria, discovering that it has been around throughout history. Scientists have documented its existence in freshwater, brackish and marine water, and discovered it hidden in fossils as well. Often referred to as “blue-green algae,” it is non-motile because its cells do not contain cilia, yet has the ability to spread via filamentous branching that bud and form new colonies elsewhere. Each cell wall is made up of a thick gelatinous membrane that helps hold it all together in the sheets we often observe in our aquariums.
It feeds on nitrogen and carbon, using the photosynthetic period to produce oxygen as it thickens visibly into a dark red mass throughout the lighting period daily. At night, it seemingly shrinks back to mere wisps of itself, but re-surfaces again the next day. Hobbyists tend to refer to this as “red slime algae,” although it has also been described as appearing blue, dark brown, or green. It commonly spreads across the substrate in the home aquarium like an ugly blanket that can smother corals unfortunate to be in its path. It may feel slippery to the touch, lifting as a thickened patch as bubbles form within it. It may form on the rockwork and on some corals as well, especially on deadened tips lacking tissue. Knowing that this bacteria is actually a normal part of natural filtration, one might think it isn’t of great concern. Be that as it may, people are quick to seek help in removing this eyesore from their beautiful tanks, and have used many methods. The purpose of this article is to provide some solutions.


Is cyanobacteria harmful to the livestock? Some animals will avoid it, while others may die if they make contact with it. This primarily pertains to snails. Very few will seek it out, although reportedly seahares may consume it, as will Red Footed Snails. Since these aren’t guaranteed to resolve the bloom, hobbyists prefer a more direct approach.

The first response usually offered to eradicating cyanobacteria is to increase flow in the aquarium, reduce feedings, and check the age of the light bulbs in use. While this advice may help some, it isn’t the blanket cure for the majority of systems. Hobbyists with excellent husbandry skills may still encounter cyanobacteria from time to time. Could it be overfeeding, a lack of water changes, or dosing carbon-based products? Perhaps it was all of the above, but in reality what has happened is that everything fell perfectly into place to create a “cyano bloom” where previously one had not occurred. This type of bacteria was already in the system, waiting for the conditions to aggregate to the point that it could finally rear its ugliness as a reddish mass, much to the dismay of the hobbyist, seasoned or newly involved.

Siphoning out all that is visible is a good way to reduce its volume in the aquarium, but it won’t get rid of all of it. Brushing it off with a tank-only toothbrush may help, and keeping the protein skimmer working at peak efficiency is another good plan. Trapping any bits floating about in filter floss or a filter sock can help reduce its physical presence too.


For those that prefer a non-chemical solution, a simple method is to simply turn off the lights over the aquarium for three days³. If the reef tank is primarily made up of soft corals and fish, proceed without fear. If the tank contains large polyped stony corals (LPS), anemones, and clams, this method is still a safe choice. If the tank contains small polyped stony corals (SPS), there may be reason to pause to consider if the livestock can tolerate 72 hours without light. Several people, including this author, have left the lights off over their SPS-laden tank and were very pleased with the amazing results. What happens is the cyanobacteria is starved without a light source, and thus dies back sufficiently that when the lights turn on again, it is gone. An additional perk is that the water clarity will be incredible; all four walls of the aquarium are completely clean of algae, and the sand and rock will be cyano-free. The protein skimmer should be cleaned out daily, especially on the third day because that is when the die-off will be exported quite heavily.

By removing the light, photosynthesis could not occur and the bacterial bloom regresses. There is no need to wrap the tank in dark plastic (an excessive approach), just unplug the lights. When it is time to feed the aquarium, turn on a nearby light in that room so the fish can see the food added, then a few minutes later shut it off again. If sunlight is splashing across the aquarium each day, curtains or mini-blinds may be a worthwhile consideration.

If a chemical solution is preferred, two well-known products available in most fish stores are Boyd Enterprises Chemi-Clean (not Chemi-Pure) and Blue Life USA’s RedCyano Rx. The chemical in either product is safe for livestock: fish, corals, clams, anemones, and inverts will appear completely unaffected throughout the entire treatment. Mix up the desired amount of the product in a cup of water, following the instructions carefully. The hobbyist turns off the protein skimmer for three to five days while the product is working in the water, slowly killing it (and possibly other bacteria) over time. It may be necesssary to add an airstone and air pump to maintain oxygen levels in the aquarium, especially in a system with low flow rates. After the cyanobacteria is no longer visible, a 25% water change is highly recommended, and the protein skimmer is turned on again. Expect the skimmer to overflow excessively the first twelve hours; the easiest solution is to empty the collection cup often, replacing that wasted water with more saltwater. On a larger tank (300g), it wouldn’t be surprising if the skimmer exported 14g of watery skimmate until it finally settled down and resumed skimming as it should.


One may wonder how they can avoid getting a cyano bloom in their display tank in the first place. As the months go by, minor changes in water chemistry may occur. New foods may be utilized, new brands of salt may be selected, pumps may not get the attention they deserve resulting in lesser flow in some zones of the display tank. Others may opt to dose their tank with vodka, vinegar, or sugar, with the desire to lower nitrate and phosphate with a known carbon source. Such changes often result in a brief (or not so brief) cyano bloom that may necessitate making adjustments to resolve that now-surfaced problem. The best way to avoid creating a problem is to make changes gradually and avoid knee-jerk reactions. If a person is dosing a carbon source and relying on the protein skimmer to maintain oxygen levels, it likely rules out the option to treat with Chemi-Clean since that product requires the skimmer to be left off. Instead, they may want to approach it non-chemically, or perhaps ramp down those daily carbon doses while they wait for the cyano bloom to die back. Being proactive is usually best, staying on top of tank maintenance and watching for any signs that are out of the ordinary. With that approach, one can spend more time enjoying their tank instead of fixing problems.

Happy reefing.


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References:
(1)http://www.google.com/#hl=en&source=...14be7db8b10649

(2)http://en.wikipedia.org/wiki/Cyanobacteria

(3)"No Lights for 3 Days Every Couple of Months Works Wonders!" - http://www.reefcentral.com/forums/sh...readid=1078532