Inadvertent Alkalinity experiment

The plants in my small tropical tank have been suffering through a snail
infestation. But they've been looking really bad the last couple of weeks,
so I know there's a serious nutrient deficiency happening. I follow the
Estimative Index for my other tank, but this tank is a bit far from the
water for easy changes. So I dragged out the test kits to see where my water
is. Turns out Phosphates were high, Nitrates were moderate, Iron was nil and
KH was practically nil. So I put some Calcium Carbonate in a small vial with
some holes in an attempt to change the KH somewhat gradually. This idea did
not work too well, as the CACO3 is dissolving too slowly. But it's making
enough of a difference that it's attracting the Cherry Barbs. The SAEs and
the Snails don't seem to care.