Based on my experience in the infertile, acidic soils of east Texas, you can add a LOT of fertilizer & fish food without even getting an acceptable bloom, much less causing excess nutrient loading. The one and only time I've ever had a really good bloom, good enough to make me worry about cyanobacteria risk, was last year after 95 percent of all my plants were killed via herbicide. (That wasn't the intent, but that was the result.) The pond got really deep green for a couple of months, viz about 14 to 16 inches, and I sweated it out until it gradually cleared up.
Am I missing something here? Maybe so ... but it seems like you had a very ugly bloom of Southern Naiad that you could not live with at all. Killing it killed most of the rest of vegetation you wanted and caused a super intense phyto-plankton bloom that according to your own measurements falls within the trophic state of hyper-eutrophic and according to the passage above made you "sweat" with worry until it subsided.
Actually, this is precisely what I am talking about. The water originally needed liming and nutrient addition but now its accumulated nutrients to the point where your pond produces too much vegetation and you've elected to resort to the feed/herbicide cycle. I respect that this is your path and that you seem to be very comfortable doing it with intentions of continuing. It's just this isn't a path I could follow myself.
Richmond Mill Lake's tremendous success, an even more infertile body of water than mine, shows that feeding can work to build a great fishery without overloading nutrients. Maybe that will change in the future, but it hasn't so far.
But it isn't just the feed. The LMB and BG are supplement stocked because they don't successfully recruit. They can control the population of LMB and BG. The water is too acid to support a good food chain so feed is only way fish can be grown acceptably in the water. Also, I wouldn't go so far as to say nutrients are not are not loading. Some nutrients remain in the lake itself without appropriate biodegradation. The rest goes downstream with the ongoing outflux of water just waiting to be mixed with other waters where it might be a problem for those downstream. Not saying the situation isn't forgiving to RML but nutrients are going in and what doesn't flow over the dam is accumulating.
I would prefer myself to have borderline mesotrophic/eutrophic water where the sun grows the food. Not saying I wouldn't use feed but I would use feed in the cells below my main BOW and use the waste water for irrigating crops.
