[SantaMonica]

Scrubbers are sized according to feeding. Nutrients "in" (feeding) must equal nutrients "out" (scrubber growth), no matter how many gallons or liters you have. So...

An example VERTICAL upflow or waterfall screen size is 3 X 4 inches = 12 square inches of screen (7.5 X 10 cm = 75 sq cm) with a total of 12 real florescent watts (not equivalent watts) of light, or half that for LEDs, for 18 hours a day. If all 12 watts (6 watts LED) are on one side, it is a 1-sided screen. If the watts are divided on each side of the screen, it is a 2-sided screen. This should be able to handle the following amounts of daily feeding:

1 frozen cube per day (2-sided screen), or
1/2 frozen cube per day (1-sided screen), or
10 pinches of flake food per day (2-sided screen), or
5 pinches of flake food per day (1-sided screen), or
10 square inches (60 sq cm) of nori per day (2-sided screen), or
5 square inches (30 sq cm) of nori per day (1-sided screen), or
0.1 dry ounce (2.8 grams) of pellet food per day (2-sided screen), or
0.05 dry ounce (1.4 grams) of pellet food per day (1-sided screen)

Problem rocks: Each 50 pounds (2.2 kg) of nuisance algae covered rocks you have adds 1 cube a day.

Flow or air bubbles is always 24 hours; water flow is at least 35 gph per inch of width of screen [60 lph per cm], EVEN IF one sided or horizontal.

FLOATING SURFACE SCRUBBERS WITH STRINGS: Screen size is the size of the box (Length X Width), and is 2-sided because the strings grow in 3D.

Clean algae:

Every 7 to 14 days, or
When it's black, or
When it fills up, or
When algae lets go, or
When nutrients start to rise