Cyanobacteria is this red snot-like bacteria that grows over about everything. Sometimes it’ll have bubbles, sometimes it won’t. It looks like red spiderwebs in the morning dew (if you live in a place where that happens).

This one is due mainly to two things. Too many nutrients, and not enough flow. (for information on nutrients, see that section above in ‘Hair Algae’).

After you take care of your nutrients, do what you can to increase flow in this area. Get a powerhead near the area, re-aim your return from your sump, or get a wavemaker. Do something to get more flow over that area of the tank.

Many people will recommend different chemicals to add to your tank, but adding chemicals is really fixing the symptom and not the actual problem. Fixing your flow issues and removing any additional nutrients will fix the actual problem. Avoid adding chemicals at all costs.