As the algae grows on the screen, it expands out enough that it makes contact with the walls of the box. This causes it to trap a little extra water, which starts a cycle of addtional algae growth that has been termed "3D" growth. In reality, all algae screens do this, but the advantage to the flooded box is that as the algae gets suspended in the water column, more light reaches the algae beneath it (closer to the screen) and so you get deeper growth. Supposedly, you can let a screen grow longer than 7 days between cleaning with a design like this, but I'm not risking it anytime soon, since this isn't my personal tank.
Here's what the screen looks like at the end of the week (this is with water running)
Here's what the screen looks like at the end of each week, right before cleaning:
...and this is the amount of algae I harvest from this system EVERY week
I've never bothered to drain & weight it or put it in a measuring cup. I should probably do that. It looks like at least 3 cups/week and probably at least 16 ounces.
Some tank parameters:
120g acrylic
40 Breeder sump
>200 lb LR
effectively about 110 gallons system water
Mag 12 return pump
Screen is approx 20" long and 7" tall
Flow rate is 433 GPH, so screen flow rate is only 22 GPH/inch, which is horrendously low. Working on fixing this.
Lights on ATS are on from 4pm to 7am (15 hours)
1 Koralia 4
2 Koralia 3s
48" 8 lamps T5HO Nova Extreme light fixture w/5 ATI Blue Plus, 2 ATI Purple Plus, 1 Geisemann Aquablue
Corals:
40 heads of Red Sea Pulsing Xenia
3+ colonies of Brown Anthelia
Green Star Polyp
Kryptonite Candy Cane Caulastrea
ORA Green Birdsnest, baseball size
Tri-color Valida, approaching baseball size
Rose millepora, pinky size
Green Digitata, 2 about 6" and several others from 1-3"
Red Caps spread out through the tank
War Coral, golf bal size
2 Frogspawn colonies, 5 heads & 8 heads
Branching Hammer, baseball size
Sun Polyp, thumb size (which is never target fed and continues to grow)
Florida Rics: Blue, Green, Tri-color
Zoas: GUNK, Watermelon, Packer, and about 3 or 4 others I've forgotten the names of
Mushrooms: Green, Lavendar, Speckled, Fuzzy
Leathers: Toadstool, Tree, one other (can't remember name)
Trumpet Coral, 7 large heads
Dendro, 5-6 heads
Fish:
6" Blue Hippo Tang
4" Scopas Tang
4" Flame Fin Tang
10" Engineer Goby
2" Green Chromis
1" Yellowtail Blue Damsel
(2) 2" Ocellaris True Percula Clowns
(2) 2" Ocellaris Black & White Clowns
5" Banded Jawfish
3" Scooter Blenny
4" Snowflake/Starry Blenny
CUC:
Lots of snails and hermits
(4) Peppermint Shrimp (maybe, never see them)
1 Coral Banded Shrimp
Water test results:
Nitrate 0 (sometimes as high as 0.1)
Phosphate varies between 0.11 and 0.2 (overfeeding until I get rid of Xenia)
Salinity 35.5-36 SG 1.027 (Reef Crystals)
KH 8.5-9.0
Calcium 420-430
Magnesium 1350
pH 7.95-8.2
Temp 77-80 (was 81.6 last weekend - need fans & controller!!)