2 replies to this topic

[Acura]

Cyanobacteria, is commonly known as "red slime" or "red slime algae". They are photosythetic organisms, typically microscopic and unicellular, although it's not uncommon to see them in large colonial formations (as any reefer who has had to deal with an outbreak can tell you). Cyanobacteria exists almost anywhere there is water - in both fresh and saltwater. It has many forms and actually can appear in many different colors, depending on the species.

Cyano outbreaks in the aquarium are quite common, almost always cause the reef-keeper considerable distress, and are actually relatively easy to diagnose and treat, if you have some commone knowledge and a little patience.

Cyanobacteria is typically called "red slime algae" in the aquarium hobby, because a large colony typically resembles a velvety carpet or mat which will cover the sand and/or rockwork. The color of this growth is often a deep red or crimson, ranging to reddish purple. You may often see fine bubbles trapped in the fibrous surface of the colony. It's often possibly to peel or siphon the cyanobacteria out of the tank, but to your dismay, you'll probably find that it grows back within hours.

The aquarist's main objections to cyanobacteria are basically: First, it is unsightly. It can cover sand and rocks and is not particularly attractive. The other threat is that it can often smother corals, outcompeting them for both light and dissolved nutrients in the water column.

Cyanobacteria has three necessary ingredients: water, light and nutrients. If you take one of those away, a cyanobacteria outbreak will fail and die, although it should be noted that small, microscopic traces of cyanobacteria are still almost certainly present in your aquarium. There just isn't enough to pose a problem.

This is an aquarium we're talking about, so you can't remove the water. Water changes are a good idea in any case, but unless you feel up to doing significant daily water changes, this is not a long-term solution. One thing to keep in mind, though, is that cyanobacteria colonies typically establish themselves in area of low water movement. While you may not be removing cyanobacteria from the system, you can at least keep it from forming large, unsightly and potentially damaging colonies by increasing the flow and circulation of water. Since we've determined that having aquariums precludes us from removing the water to get rid of cyano, we turn to light and nutrients.

If you don't have any corals (many of which typically require at least some light), you can reduce or completely remove your lights (at least temporarily). You've probably noticed that in the morning when your lights come on, the cyano is mostly (or even all) gone, but as the day goes on, it spreads rapidly. It's possible that aside from reducing your photoperiod, a bulb change is in order. Old bulbs shift their light spectra to a different wavelength, and this change can spur changes in algae and bacterial growth.

However, the best way to treat cyanobacteria is by limiting the introduction of nutrients and encouraging nutrient export.

You limit nutrients by feeding less. Cyanobacteria thrives on the nutrients produced by rotting food (especially flake food, which is often high in phosphates). Feed in very small quantities, and watch the fish closely. Stop feeding the moment any piece of food hits the bottom of the tank without a fish eating it. If you have food falling to the bottom of the tank, you're using too much food (unless of course the only fish you have are bottom feeders).

Nutrient export is achieved several ways. The most common is protein skimming (also known as foam fractioning). You can also use activated charcoal products (GAC), though it should be noted that many peoples' experience with such products is that they should be used for short periods of time and removed, because the crushed media inside the filter bags provides a huge surface area for nitrifying bacteria to grow on, creating what's known as a "nitrate factory."

Perhaps the best way to export nutrients is to install a refugium and grow any of the fast-growing macroalgae species in it. What happens is the macroalgae (plants) absorb the nitrates and phosphates out of the water (nitrates and phosphates are the key ingredients in fertilizer and are more commonly known as plant food). As the plant grows, you clip some of it off and dispose of it. It's like a sponge - it soaks up nutrients, and then you take the plant (which is full of those nutrients) out of the system (and take the nutrients with it). There are other benefits to having a planted refugium. The algae helps with oxygenation of the water, which can help to stabilize pH and keep your fish happier. The algae may be eaten by various residents of your tank, ranging from crabs and shrimp to certain fish (depending on the type of algae you get to grow). The algae also provides a fertile breeding ground for amphipods and copepods, which are typically very desirable as scavengers as well as food for a variety of fish (especially mandarins and the other members of the dragonet family, which specialize in eating only copepods when found in the wild).

There are, of course, other methods of dealing with cyanobacteria; namely the use of medications and chemical treatments. e.g. Red Slime Remover. Extreme caution is urged, however, when using Red Slime Remover or other chemical or medicinal treatments in the aquarium - it's important to recognize that the health of your aquarium depends very much on the establishment and cultivation of a variety of nitrifying bacteria which lives in your live rock, sand, filter media and many other places within the aquarium system. Chemical additives often work on the principle of being an anti-bacterial agent - that is, they kill bacteria... indiscriminately! These chemicals may be exceedingly effective in eliminating a colony of cyanobacteria... but may also kill the many beneficial types of bacteria that keep your tank's inhabitants happy and healthy. It's highly recommended, therefore, that chemical additives be avoided in favor of other means of treatment.

References:

1. Cyanobacteria: Life History and Ecology
2. KINGDOM MONERA: The Cyanobacteria

[blueheaven]

Just a note to add on to this topic
Commercial products that remove cyano are usually just antibiotics so it will definately affect the different forms of bacteria in your system.
I'm not saying that they don't work but just that they must be used with extreme caution :)

[Acura]

blueheaven, on Nov 17 2005, 09:19 PM, said:

Just a note to add on to this topic
Commercial products that remove cyano are usually just antibiotics so it will definately affect the different forms of bacteria in your system.
I'm not saying that they don't work but just that they must be used with extreme caution :)

That antibiotic u mentioned is commonly referred to as Erythromycin. Erythromycin is often very effective in killing bacteria, including cyanobacteria. ;)