ac7av
Bring on the FISH!
What I think is happening is a case of old tank syndrome. Some times in an established system if the proper up keep has not been preformed for that tank for a long time or inadequate skimming you can just basically clog up all the rock and or sand in the system with too much “junk”. Water changes would do nothing for this and lowering the light per day will do nothing as it is only a temporary fix. The cause has to be eliminated. When you go back to normal it will just come back. Old bulbs will not cause this to grow any more then new bulbs will. I think after looking over your thread that the only way to really fix the problem is to do a thorough cleaning and if you use a canister filter to collect the free floating partials and GAC to help clean the water is what it’s going to take IMO. A refrugium is the best control of this type of algae or bacteria. You can also just wait it out. When it uses up all the nutrients in the water that its consuming it will die off but that may take a while and if you have any corals in your tank that would not be a good thing to have it covering the corals. Using a UV sterilizer will also do nothing for this kind of condition. The bottom line is way to much organic matter rotting in the system for the system to keep up with it. You need to get it out.