The science shows that mercury can kill candida just as it can any other living organism. It also shows that candida can take elemental mercury and transform it to methyl mercury. I've never seen anything about mercury causing candida or feeding candida.
Mercury can cause immune system oppression which can factor in as an effect that might make I easier for candida to thrive in it's fungal form.
Many candida and heavy metal symptoms are the same, and both usually exist in the modern human body, and both usually need to be treated.