Potassium permanganate

The FAQ mentions this as a good method for removing snails from
plants. I've been asking at various drug stores but have had no
luck in obtaining this stuff. Anyone know of an alternative source?
One pharmacist said they no longer carry it because it makes an
excellent explosive. Hey, this could be handy. Might have another
possible application here; the removal of unwanted brush algae
(and plants, fish, water, tank, lights, spectators... ;-)