A couple of years ago my upstairs 33 developed issues with cladophora. I tried everything short of CO2, but finally gave in. It did the trick, until it didn't. My tank isn't empty, diffuser is still working fine, lighting (current satellite plus) hasn't changed, plants and fish are all healthy. I even tried reducing light hours. What else is there to try?
I can check. Usually not, but I suppose it's possible that something has changed. I did go ahead and clean the filter sponges, which might have contributed to something like that. One side looked pretty good, but the other looked like I'd missed a cleaning. I did step up water changes a bit, but it hasn't helped.
Has anyone experimented with Fluconazole? I've heard good things about it on Bryopsis, which is a marine hair algae. It doesn't bother higher marine plants or zooxanthelae, but I have no idea what it'd do in a sweetwater tank.