You don't need to vacuum Floramax... but, I have done so after like a year when the mulm has gotten so thick. I do it when I feel I need to pull out ugly stem plants when the bottom of the stems has had all the leaves fallen off or deteriorated. After I do a light vac, I'll replant the top of the stems where the plant looks best. I'm not sure if this is even necessary...but nonetheless, I feel better and my plants grow just fine after the fact.