Interesting stuff Carey. It's amazing what was acceptable years ago, isn't it?
Custom "blended" bacterial slurries sound extremely expensive, but I don't have any frame of reference for that.
Through my testing in the lab here in Florida, I haven't run across too many situations that have nitrogen problems, unless there's been a spill of some sort or as a result of a massive fish kill caused by something else (oxygen levels usually). My point was actually that it was a neat "side effect" that added nitrifying bacteria either also worked on the muck, or altered the situation enough for another strain to work on it.
As for water changes, ponds don't really get true water changes unless they are drained and refilled, or are fed by some source and have a spillway. All rain and evaporation will do is dilute and then concentrate the waste products in the pond. Evaporation is only water vapor, not the waste products. They stay in the pond as the water evaporates (kind of like boiling salt water and ending up with salt in the bottom of the pot). What you need in order to do a true water change is a way to physically remove the waste products as well, and then bring in clean water. But most ponds have more than enough bio-filtration naturally and would never need a water change.
