It's very likely that what phosphate you are producing is being consumed by the algae as fast as it's being made. Also, one trick I've heard of is heating your sample water to 80 degrees celsius and then testing again as that often gives a more realistic measure of your phosphate levels.
As for the pics, try setting up a photobucket account at
http://www.photobucket.com. It's pretty easy to upload there, and once the photos are on photobucket you can just post links to the image in the forums which will make them display in the body of your post rather than as links that people have to sign in to view.