So, my display and my sump are two sides of a coin. My sump has a powerful refugium light on it, and I let whatever algae grow that wants to in it. I have tuxexo urchins (4small), trochus snails (5 to 7), couple of ceriths, and 4 tangs and a foxface. The tank is 525 gallons. I know I have hair algae, it grows like crazy in the sump. Along with the sea lettuce. I just trim out of the sump for export and let it go wild. The display? Some mild green film on the glass and some of the rock, but it stays in check. Get a good refugium up and running. It'll take a bit of grooming the display with cleanup help, but you should be able to beat it with diligence, patience, and a game plan without chemicals. I also think dosing live phytoplankton also was a big help going through the uglies. The chemicals may be keeping you stuck there. But also consider the algae living somewhere to do it's thing.