I know this is a very popular method among reefers, but it doesn't directly apply to FW planted setups.
I have played with growing algae in a freshwater sump to control it in my tank, and was unsuccessful at it.
But still am intrigued by the idea. After reading the thread "healthy plants = no algae WHY??", it seems more is known about what does not cause algae (ie. high N03), but ultimately not what causes it.
The fact that excess nutrients do not cause algae, does not disprove that growing algae to control it would work. Nor does it prove it.
Great Thread! Thanks for the info.