Whle all of the previous suggestions work, you need help.
There is another way to get the algae under control. It's called an ATS or Algae Turf Scrubber
See the DIY thread suver569 and pazhope have going in the DIY section.
IF you are a DIYer and have a drill, dremel tool or grinder and a few bucks you can make one yourself from a bucket, compact fluorescent light and some PVC pipe. There is plenty of information on that thread with links to the whole evolution and history of the ATS.
How much you feed, how long your lights are on will no longer be a problem with a properly functioning Scrubber and even the worst algae overgrowths can be handled in 12 weeks or less. If the water changes can't handle the phosphates they can build up in the rocks like a sponge and even if you can't measure the phosphates they can still leach out of the rocks right where the algae can get to it. After a while the scrubber will out compete the algae in the display for nutrients and the unwanted algae will start to go away.
Oh yea and that is all with no PROTEIN SKIMMER!
I know... it sounds crazy... and some will say it aint so! some will go so far as to call it SPAM! but why would it be spam if you make it yourself?
All I'm saying is there is another way and I hope you have not thrown in the towel yet. I only got back into the hobby after 20 years because I stumbled onto the ATS on another forum while trying to help a friend get his tank under control.
It's working on my tank and that is all I have filtering my water.
Hope this helps,
thanks for your interest,
Brian