Thank you esshup, I appreciate your perspective. The question of when a bloom is dangerous to fish or has created conditions where a kill is imminent has always intrigued me. One of the things that perplexes me is what are outcomes of various treatment and what are the outcomes if untreated. For any case, we can't really say when one path is chosen over another. We just don't know because we chose one path and didn't allow a different path and so what would have happened is a WAG.
After reviewing the pics, I notice that the OP has been sodding the dam and that he thought fertilizer laid for this has washed into the pond. I originally thought it was the yard he had fertilized. I still remain puzzled as to the weight of fertilizer used and the footprint of the pond and just don't yet have sense of the nutrient density. The 46-0-0 .. I wondered if he meant 0-46-0 where the nutrient was phosphorous. If so, this 69 lbs of phosphorous (if 50 lbs/bag) is probably the primary contributor to the bloom and is excessive as a single application. The question is how much got into the pond.
Most members here seem to have bows well along the path of eutrophication. This saddens me to some extent. To have a pond that is well along the path of dying after only a few years of age seems to lack appropriate stewardship unless the soil itself or other uncontrollable factor is the cause. In the OP's case, I wonder if the remedy is any better than letting it run its course. What are the risks of killing fish by controlling the bloom? In other words, is there risk of depleting oxygen by killing the bloom. Is it cheaper to repurchase the fish or apply the remedy in a 1 year old pond? If there is a time of year that one can be patient with a bloom like this ... it is this time of year when water temps are moderate and the daytime length is long and getting longer. Anyways, one has to choose a path and if one does nothing about it and there is a kill he will probably always think it was the lack of action that did it. If one does something about it and there is a kill, some will say he didn't do the remedy correctly and that they would have died anyway. It is a kind darned if you do and darned if you don't scenario. I hope whatever path the OP takes it works out well.
