The lime dosing I saw was addressing acid mine drainage, which is probably a different issue than just a naturally low pH stream.
Low pH usually means less invertebrates such as insects because less calcium is available for their exoskeletons, thus less insects as a food source for trout.
Acid mine drainage affects that also, but has the addition of solubilizing heavy metals which become toxic to fish and probably insects. Lime dosing is as much targeting tying up toxic metals making them less soluble.
I am not sure of the harmful effects of lower pH on fish or differences of tolerance across species.
Dumping limestone in just about any form will eventually be dissolved by low pH water just that the finer it is the faster it dissolves. I wasn’t aware that it could actually seal off from dissolution in certain situations, but I suppose anything is possible.
