[cheeks69]

Cyano is a hybrid, a mixture between plant and bacteria. It has therefore plant, as well as bacterial characteristics and is considered the evolutionary link between plants and bacteria. The “algae-bacteria” is always present in each setup. Cyano is unicellular. It cannot be detected even when using a common microscope. What can be seen as slime are thousands of cells bound together by a protective slime coat, while some break away floating freely in the water.

Cyano, being a hybrid, is difficult to remove. Factors for growth are multiple and dealing with the algae-bacteria needs to be on multi levels in order to be effective.

Growth factors include, light, nitrogen-nitrate, dissolved organic carbon, and CO2. All of these factors are basically interchangeable, meaning that one or two factors can be limited, but it won’t stop the algae-bacteria from utilizing the remaining factors, nor will it stun their growth. For the sake of completeness, some limiting factors influence the shape and appearance, but not the occurrence itself.

Light might be an obvious factor as Cyano is able to photosynthesize, but eliminating or reducing the light will not stop the growth. Recalling that Cyano is a hybrid, it will rely on bacterial characteristics to produce energy for growth. Reducing the access to carbon as an alternate approach has no effect by itself either, since the algae-bacteria can use CO2 as a sole carbon source.

Robert Fenner:

It should, must be stated that even given the usual measures of nutrient availability showing low concentrations you may still run into Cyano problems… they’re actually fueled much more by DOCs, dissolved organic carbon compounds… hence the careful cleaning and use of a decent protein skimmer as a first line of defense, limiting DOCs in your water. And, ahem, where do these celebrated DOC’s come from? Principally (over)feeding. Be especially leery of liquid invertebrate and gelatin based frozen foods… these are notorious sources of DOC...
...Filtering water involves all we do to modify its make-up chemically, physically and biologically. This being stated, by doing your best to remove excess nutrients like phosphates and nitrates (through periodic use of chemical filtrants like activated carbon, keeping your skimmer optimally clean and operational). This is a key approach to BGA prevention as "higher" photosynthetic life forms are far more able to survive and outcompete Cyanobacteria at lower nutrient level concentrations.

Aeration/Circulation

Cyanobacteria thrive in low circulation, poorly aerated conditions. Hence the call for vigorous water movement and near-saturation levels of dissolved oxygen. Providing powerheads, small submersible pumps, mechanical aerators and directing discharges from outside filters and pumping mechanisms are the best way to accomplish optimized circulation and aeration. Direct these devices to eliminate stagnant areas.

BGA Control

Despite their best plans and actions aquarists frequently run into some Cyanobacteria problems, especially when their systems are going through initial cycling and settling in. There are a few appropriate responses to these situations, and one that is often employed that you should (and will) be advised against. Here are the suggested controls.

Elbow Grease:

Gingerly wiping the slimy colonies from the tanks sides, regularly removing the mass of the BGA from the gravel and décor surfaces goes a long way to removing the BGA and their ill-effects.

Cyanobacteria