No way I would use corn gluten for algae based on the info so far. If it is N as per your post it may not help with pond fertility as per Greg's comment (most of the time the limiting factor is low P not N ) .

The web site says it ties up P in the pond as a method of denying FA nutrients. If so it can't help with pond fertility because it is tying up nutrients. This also is contrary to the life cycle of FA. By the time FA gets to the surface it does not need nutrients as it is near the end of its life cycle. It does its growing on the bottom. Surely they are not suggesting one spread hundreds of pounds of corn gluten so it will sink to the pond bottom and effect FA. Am I missing something here?