You can build or buy a reactor for phosphate or any media and it will greatly increase the effectiveness of the media. Phosphate is the reason for your algae growth. I designed and built the DIY reactor in the link below and my problems went away. Filter socks suck because the water pretty much just runs around the media instead of through it.

Try this for a DIY thread:
http://www.captivereefing.com/showth...5303#post35303

Check out this reactor:
http://www.thatpetplace.com/Products.../Itemdy00.aspx