Cyano - Options on how to get rid.

Flow has no bearing on cyano directly, but it does help reduce the gas boundary layer around the cyano, thus making gas exchange better.

There are a lot of myths that surround Cyano. This leads to some wrong thinking when it comes down to it's causes within our marine aquariums.

Firstly, you don't need any nitrates for cyano to grow. This is because cyano has the unique ability to be able to directly utilise nitrogen, whilst in it's gaseous form. Cyano is the only living organism capable of this.

Secondly, flow doesn't affect cyano directly. More on this next.

Cyano cannot utilise nitrogen in high oxygen environments.

So, with all this borne in mind, what can we deduce?

Nitrogen......have you noticed how cyano likes to live on the sand?

There is a reason for this. Sand beds tend to be denitrifying, which is a process whereby bacteria strip the O3 from NO3 to then respirate and release the N as N2 gas.

As this percolates through the sand, guess what is there to grab it?

So, this is why you can have zero nitrates and still have cyano.

Flow has no bearing on cyano directly, but it does help reduce the gas boundary layer around the cyano, thus making gas exchange better. This in turn supplies more oxygen to the cyano, which, as stated above, depresses the cyano.

Higher Redox has the same effect, which is why ozone is helpful.

Light is essential for growth, and green and yellow light seem to produce most growth, and red is reflected, which is why just using actinic depresses cyano.

Cures.......

Erythromycin is a gram +ve antibiotic and cyano is a gram +ve bacteria.

Most "bad" bacterias are gram +ve, whilst the goodies are gram -ve. This means that erythromycin is well suited to getting rid of cyano without unduly affecting the good bacteria (with normal dosing).

Erythromycin is so effective that it can be used at half to one third the strength used for fish treatment.

Bacterial cures....sludge busters etc. These simply clean up any rotting organics in the system to outcompete the cyano and remove it's food source.

Bio Pearls.....similarly, the captive carbon source will outcompete the cyano for nutrients and in the longer term, clean up the sand beds etc, so that much less denitrification takes place. This is replaced with Nitrate export instead.

Low lights. This is only a temporary cure, as it doesn't address the actual problem, but simply removes the energy source from the cyano, so that it cannot grow.....but it will return at some point.

I hope this will help with peoples understanding of cyano, which is a fascinating organism and one of the earliest form of life on earth.

Article by Tony (Karnivor) | Photo - Whipitup

Also Tim Hayes has added new article on Reef Ramblings: Controlling Cyanobacteria in the Marine Aquarium.