Ken,
I don't think the standing weight of fish or craws is a problem. But your comment:
I think I'm in a situation where the cause is likely the cold snap we had in late september (teens for 2 days with snow) and after that we had a terrible explosion of algal growth, in part due to fallout of ash from colorado fires. Water temps dropped 30 degrees in 2 days then only rebounded back to barely 70. Water never did clear back up after that.
This causes me greater concern. I think most are unaware of just how high a standing crop of phytoplankton can become. The standing crop of algea can easily become > than 20 to 30 times the weight of fish or more. Even a small standing crop of algea can produce a daily crop of algae that exceeds the fish standing weight. Generally there are organisms that are cropping algae preventing its overabundance. This cropping also makes the metric of algae production difficult to determine because production is often unrelated to standing crop when the system is cropped heavily. Higher trophic organisms expose this production by demonstrating growth and maintenance requirements that ultimately depend on algae production which is not evident in the algae standing crop (e.g. deeper secchi).
From your observations, I think it is a plausible argument, that the cold snap prematurely seasonally shut down the zooplankton that normally crop the algae later into the fall. The algae populations bloomed subsequently but the populations of zooplankton could not recover to crop the algae. Now whether a die off of a large standing crop of algae killed fish ... I cannot say but I do hope this did not happen. I think it would be great, for cases of excessive algae standing crops, to have a treatment of organisms that can efficiently crop the algae while providing food for the fish and crays.
