[Myka]

Iron certainly does feed cyanobacteria (and pretty much any algae too), that's not a big discovery.

What I don't agree with is the iron being the trigger for the cyanobacteria. My opinion, based on my own experiences as well as hearing/reading talks by leading aquarists/biologists is that it is the imbalance of phosphate between the water column and the substrate that is the trigger. It's nearly impossible to keep cyanobacteria out of a reef tank, so it's the trigger for the explosion that you want to avoid. I've seen cyanobacteria in new tanks where old rock was used, and new saltwater was used. Also causing this imbalance. No GFO.

Cyanobacteria is certainly in the water column when it is on the substrate/rock. Think of the cyanobacteria clinging to the rocks like the fish swarming for the food. Most tanks have enough water movement so the cyano can't form clumps in the water column, but it certainly will if the water is not moving enough. In cases where there is a lot of cyano, I've often seen it floating in clumps in areas of low flow.

Keep in mind there are thousands of species of cyanobacteria.