Red Slime Algae

[supersmile]

I am having a problem with red slime algae. I have been told by a LFS to use the Red Slime be gone medication. I have used that twice now and it seems that the red slime just returns in a matter of 2 weeks. I try to siphon out as much as I can but it still comes back. Does anyone have any other suggestions? This is driving me crazy. I have gotten my water all tested and everything is fine.