Coraline Algae

[Aquattro]

The best product is time. Just wait and it will grow. Then you'll post asking how to get rid of it As it grows on the glass, scrape it with the side of your scraper and the "dust" will seed other areas. Spend your money and real supplies like salt and Ca/alk supplements.

[Madreefer]

A good source of mag is Epsom salts mixed with Absolute Zero Meltdown. If I remember correctly it's 11 parts Ice Melter to 1 part Epsom Salts. Everyone gets scared and stays away as soon as you mention using something you throw on your driveway but trust me it works great as a surce of mag.