Cyano bacteria could be either a gram-positive rod or gram-negative rod. This can only be identified & determined by an actual gram stain. Sometimes, you can exhaust all practical means and measures, with no progress and loads of frustration. Water movement, lighting & DOC's all play a factor in this equation. However, in doing all these changes, it may not totally eradicate your problem. The bacteria may go away in a few days, only to return a month later. I always try to first start with the removal of DOC's and increasing overall circulation within the system. I would then move on to the lighting (age of the lamps) If this fails to accomplish your goals, you can always go to your LFS or online and order some Red Slime Remover. A fairly good antibiotic to destroy the bacteria. This may be your only recourse. IME, I have tested a few different antibiotics on the market, and IMHO, cephalexin, AKA: Keflex works very well in ridding your system of these bacteria. 2 - 500 mg capsules dissolved in luke warm water (r/o - distilled) and dripped into the system (turn off your skimmer and take the carbon out of your mechanical filtration) will rid your system within a few days. Sometimes a second dosage is necessary for total elimination, although, rarely needed. You can start up the skimmer a day after your initial dosage.
Good Luck