Many people start out their new saltwater tanks with a new scrubber, which is fine, but they do not understand why the rocks and sand start developing growth (usually brown coatings) first, before the scrubber does. This is because the rocks and sand have some stored phosphate in them, even if they are new, and the scrubber does not. So part of the beginning of a new saltwater tank with live rock, especially if it also has aragonite sand, is that you will need the rocks to "color up" with some color of growth before expecting a new scrubber to start growing at all. Then, after some of the rock is colored, much of the stored phosphate will have been used up by that colored growth, and the scrubber will then start growing.

The first scrubber growth in these new tanks (with new rocks) will usually be a very light tan color growth, and this may take several weeks of seeing just solid white. Minimal light is needed because the white surfaces will reflect all the light and make it stronger, and, the tan growth does not block much light. So any scrubber should be started with less light: HOG and SURF scrubbers should be half shaded with a black cloth, and run on low power if provided; RAIN scrubbers should be started with just 1 light plugged in; DROP scrubbers should have the black shade screen installed; and SLIP scrubbers should have the black shade clipped on to the light, and the screen should be installed with the light-blocker on the light side so the light is blocked. Other brands of scrubbers should have their light reduced according to how they operate; if no method is provided, just use a black cloth over half of the light, or plug in only 1 light.

Once a tan color appears on the scrubber's white growth surface, and has been there for a week or so, it can be brushed off and the growth repeated for another week; this time, the growth should be darker and thicker. More light can be added as the growth gets darker or thicker; if too much light is added, there will be no growth at all.

If you get growth rings:

And about now, you will start growing periphyton on the rocks...