I am not an expert but I've battled hair algae twice, and it's always been because of the water. I was buying RO/DI from my LFS, and each time I did a water change the algae got worse. I had strands that were 2 to 3 inches long. When I had the store's water tested at another LFS, it turned out to be worse quality than tap water! I think the guy was pushing his filters way past the limit. Now I have my own TDS meter and RO/DI system. If you are buying your water, you might want to try another store. If you are making your own, have someone test it for you. I also found a phosphate pad helps a lot since that is the cause of the algae. Phosphates are hard to test for. You need a really good test kit. It's important that you find the source of your problem. It could be the food you are using, overfeeding or poor water quality at the source. Bad bulbs can also cause algae. Also, I could not find anything that effectively ate hair algae, and I tried snails, crabs, fish, nudi brachs and urchins. They ate every other type of algae but not the hair algae. Don't buy an urchin. They are not really reef safe. I tried two different varieties, and now they are both in my FOWLR tank. One kept rearranging the tank, and the other was eating my zoanthids and favias. Good luck. It's ugly and frustrating, but you can get rid of it.