I use this product from General Hydroponics called florakleen and use it at the end of the flowering cycle. I also stop using any nutrients, just keep adding water to the reservoir for 2 weeks lowering the PPM of the water gradually until I reach a number in the 400 ppm then I use the flora kleen, then no water for a couple days and cut:rastasmoke:.

SO YES VERY IMPORTANT TO FLUSH !!!:thumbsup:

pd. There are many cleaning additives , I just use this one but there are others out there.

Peace :hippy: