When it comes to water tests, I am a Saliferts best friend
I test for most things on a very regular basis. Probably overkill, but does not take long and it's part of my routine. I have tested both my tank and my make up water for Phosphates and Nitrates (both are at zero). I don't feed my tank a lot of flake food, I always do a tiny amount and it is always gone in a matter of seconds. If they are still hungry I add a bit more. This goes with all the food I give the tank, and as far as I can tell everything always goes right away. My tank has been sent up for almost 2 years now, and this is the first bad case of hair algae I have had. I know that the test kit for Phosphate does only tests for one kind, so there is a possibility it is in the tank. I took Christy's advice and picked up some Kent Phosphate Remover, last night. I am hoping that this, combined with hand removal and a couple more water changes will soon make this go away.