Like many pond matters it is a question of balance. WRT the article above it repeats a misconception as to recreational ponds , that is if you want fish. Removing all the P by bonding with Alum is not a good idea for the food chain. No P - no plankton (bottom of the food chain). There is usually one big difference between fish ponds and waste water treatment ponds - one is good for fishing the other not.

I like fish so IMO alum is not the way to treat FA. Alum when used correctly is a good tool to treat clay turbidity.