I assume this is not a regular cleaning; maybe you stored it for a while, or got it used.
To get any scrubber back to new, the growth surfaces do not really need deep cleaned; the old growth will just rot and fall off. But if you want you can use vinegar for a few hours on the rocks and strings. Then if you want white, you can use 20% bleach with water, on the rocks and strings for 30 minutes. Rinse well.
It will require low-power (1 plug) to start, and probably also the black shade cloth, because the white surfaces will be too bright.