With all things being equal, for me it comes down to expense and ascetics. Why replace perfectly good very large fish that the great grandkids are thrilled to see and that also keeps the submerged plants in control, plus the expense of smaller replacement grass carp that eat no more total plant vegetation then their larger cousins.
Esshup I'm sure you have an argument for the biomass. But it would seem to me that biomass would have to be measured in a pond's water volume by the kinds of food available. Vegetation for grass carp, algae for the KOI and Israeli carp, minnows/frogs/bugs for predators and veg.and minnows for channel catfish. At long as the large GC weren't eating what the bass were eating the biomass could become larger then just a predator pond alone. Until my total winter fish kill five years ago I had this kind of pond. I'm sure I raised eyebrows when I mentioned the number and size fish in my one acre pond which must have been off the chart when figuring biomass but the reason was, I believe, I was utilizing every food source almost possible for a pond.
