Once again something Lusk told me, in addition to comments by Bill Cody lead me to a statement that rarely seems to be addressed on this forum, in relationship to it's importance. And that is water replacement.
Lusk's one thousandth post "Wettie" talked about water being the universal solvent, but when it evaporates it leaves all dissolved substances behind in the pond. In my opinion, ponds that have water replaced by runoff events, or wells withstand higher densities much more effectively than a stagnant system.
Bill is certainly right about how the bad stuff is processed by plants and nitrifying bacteria, however in a static pond with no water replacement, plant communities can undergo significant and sudden changes that bring about the dreaded "fifteen" minutes. When I effectively replace water in my smaller ponds by runoff or well water, I never have a crash no matter how high the densities get.
Imagine how much water per fish and per pound of fish is being replaced in an aquaculture system!! In a raceway the water is replaced sometimes many dozens of times a day. That's why the high volumes of fish. If you can reproduce this even in the smallest of ways in your pond you become less at the mercy of plant community waxes and wanes.
In other words, you don't have to be as much of an expert to avoid the fifteen minutes if you have a significant and regular influx of fresh water.
Imagine if your household had to reuse the same water over and over! You'd have all sorts of headaches trying to use bacteria and sunlight to sterilize your used water to a point of reuse. Your family would be much more susceptible to disease and poor health. Ponds can be very much like this if you let them. If you're maintaining high fish densities, feeding frequently and not harvesting, then your fish need new water or almost perfect management of the plants and nitrifying bacteria. Otherwise your fish are effectively living in their own toilet.
And this is why I think discussions of "carrying capacity" of a pond can be rendered moot. The number of pounds of fish per acre maximum can probably vary by 1000% depending on water quality, nitrification, oxygenation, and water replacement factors.
Here's that great post!
http://www.pondboss.com/ubb/ultimatebb.php?ubb=get_topic;f=20;t=002424;p=1#000000
