Growing algae in open ponds is akin to producing them in a shallow swimming pool, Clarens said, so all of the nutrients — nitrogen and phosphorus — needed to keep them alive and boost their production come from outside sources. (scientificamerican.com)
We also build large open pond algae farms and use these to capture carbon and sequester it permanently (see my other post in the @Fran Barlow Hansen thread). (johnquiggin.com)
As mentioned in work discribed on page 147, maintaining the proper culture in open ponds is difficult. (realclimate.org)