I am not that person; but I’d be curious to know how koi would react to such a corner-case environment. Fish presumably didn’t survive this long by being incapable of sensing lack of oxygen(or at least CO2 buildup); but they also evolved in an environment where the oxygen gradient is almost always such that ‘up=more oxygen’. In the case of a suitably large dome, in an otherwise normal pond, the reverse would be true.
Would the koi figure it out(or at least adjust sufficiently quickly and reverse course), or would their low-oxygen heuristics doom them by causing them to seek to rise to the surface where the oxygen should be most abundant, and instead end up in the most-depleted zone at the top of the dome?
