Thanks Bill, great post!
One thing that I didn't elaborate on is the food. jpsdad, here is some info that I didn't post, that leads me to believe that the reduction in FA that I saw the first year of switching food brand wasn't coincidental.
A PB member here did a feed test in which he had (roughly) the same number of fish in a cage, of the same size and weight. IIRC 3 different cages with identical "standing crop" loads. 3 different feeds. He monitored the fish and the food that was fed to the fish. He was specifically looking for how much food to feed to achieve the same weight increase in the fish. His results were (again IIRC) 40# of Optimal BG or BG Junior feed, 60# Purina Aquamax 500 or 120# of Sportsman's Choice from TSC. all put the same amount of weight on the same amount of fish.
I am not familiar with that feed test. I do know that Greg Grimes posted results of test that sounds very
similar to the one you refer, however, Optimal was notably absent. Instead Purina Aquamax topped his list at an FCR of 1.85. At the bottom was Purina Game Chow with an FCR of 3.22. If the referenced test achieved a 33% reduction of feed inputs over aquamax, and if Greg did a fair determination of FCR for Aquamax, then the FCR according to that other PB member for Optimal is 1.23. Given my respect for Greg, I am skeptical of this claimed FCR of 1.23. I think PB members without a pig in the poke should try to replicate these results. Not to expose any bad science but seek true knowledge because that FCR (1.23) just doesn't make sense for BG of the sizes that Greg grew.
I switched from Purina to Optimal and saw the difference. Was it coincidental? Maybe, but then again maybe not.
If it coincides, it is coincidental. The thing to remember, is this, we want to understand causal relationships. Causal relationships also coincide and are therefore also coincidental. Co-occurrence doesn't demonstrate causality and especially when the presumption of causality rests on invalid assumptions or violates other known truth.
I was able to reduce the amount of feed going into the pond by 33% and still have the same fish growth. I have observed the same lower level of FA growing in the pond ever since switching food brands. So in essence I reduced the amount of nutrients going into the pond.
Not really. You have reduced feed input but this could, without other mitigating factors, increase the nutrients standing from year to year. If your nutrients are not increasing but leaving the pond at the rate you are adding in feed, then these factors ... or other factors like TP use, progression of the plant community diversity, etc ... are responsible for the modest FA you have seen since changing feed.
My response to the anecdote was intended for everyone and so I am also urging you too to be skeptical that the observation has a causal relationship with the change of feed.
By reducing the weight of feed by 33% going into your pond, you did no doubt reduce the
accumulation of nutrients relative to the 'imagined continuation' of the prior weight of feed . You may have a case, though I am not fully convinced, that one brand of feed will create more gain on less feed. Even so, one of the pieces you are missing is the manuring effect of feed which doesn't come into play in cages. This effect can greatly enhance growth by increasing natural foods. I'm not convinced either that more nutritious food wouldn't result in more nutritious waste. From my perspective, the argument that more nutritious food results in less nutrients in waste reaches too far without corroborating evidence under controlled conditions. This would be necessary in order arrive at sound conclusions about this hypothesis.
In cases where nutrients are not excessive, I would not in any way discourage feed use. On the other hand, when they are already excessive ... then that is a different situation. Using feed ... no matter who manufactures it ... cannot be a remedy for excessive nutrients. If the nutrients are excessive ... and one feeds in spite of this ... then he can go about mitigating it, as I said before, by whatever means are available and desired to find his remedy. To be sure, we shouldn't categorize these actions independently (TP, GC, binders, herbicides, dye, plants, raking, etc.),
they are all a cost of feeding a pond with excessive nutrients. In this sense ... once the nutrients are excessive ... feeding becomes the tail that wags the pond dog.
