The redstuff could be cyanobactor. This is a form of highly undesirable algae that will blanket every surface in the tank. To remove it you can take a syphon hose and suck it out of the tank. It shoudl com off very easily.
Is your tank new? Do you know what your water readings are? What kind of water are you using to make saltwater with?
__________________ Remember dont tap the glass, your fish will think you're an idiot-Anonymous mother