I do, and here's how I do it. I take the old potting soil, put it in a 3 gallon pot, and pour a kettle of boiling water through to kill it, then I mix it half and half with new potting soil. Things grow very well in this, and I've never had any root rot problems from the old soil.
Didymo (Didymosphenia geminata), also known as rock snot, is a non-native invasive microscopic algae (diatom) that can produce large amounts of stalk material to form thick brown mats on stream bottoms.
Itâs a microscopic alga known as a diatom thatâs invading our rivers and streams. Didymosphenia geminata, also known as ârock snotâ or âdidymoâ, can smother entire stream beds with mats as thick as eight inches and can ruin just about any river or creek.