Need to grow huge quantity of algae/plankton FAST?

Question

I need to create artificial waterbodies -containing clean rainwater- few hectares- and more or less cover it with THICK algae/plankton FAST- to provide food and oxygen for aquatic creatures as well as thick humus layer to areas irrigated with this water. The natural process is very slow. Can you help?
Are there algae/plankton seeds available that dont harm water quality/aquatic life and propagate real fast?

Answer 1

Consider reed beds, much quicker and more efficient.

Answer 2

Yes, we do, to counteract global warming.
If you do find out, don't tell GW Bush.
He'll say it helps terrorists.