Hi my name is Karen and I have had the same problem.
Do you have a low water level in your filter box? My pump used to suck in water with air when the water level was too low from evaporation, compress it together and then pump it into the tank via a pipe which was just below the water surface. This gave my seahorses GBS. I even had the same red algae problem and the air bubbles stuck to the sides of the glass and to the rocks. Is air being sucked into your water during the filtration process?
I also had a quite knowledgeable local aquarium which could mind my fish for me in their tanks if I went for a holiday or if there was a problem with my tank. (depending who it is, they may be more interested if they are paid). This was a disease risk, but if the problem is coming from your tank then could this be an option?