DIY Algae Scrubber (ATS) for Nutrient Export
An algae scrubber outsources the algae growth from your display rocks to a dedicated chamber. The algae consumes nitrate + phosphate just as efficiently as GFO without ongoing media costs.
How it works
A textured plastic screen (3D-printed or knitted) sits under intense red+blue LED light, with water flowing over both sides. Turf algae (filamentous green) grows on the screen, consuming N + P. You scrape it off weekly. Net result: nutrient export without skimmer or GFO reactor.
Sizing the ATS
Rule of thumb: 1 sq inch of screen per gallon of system volume, OR 0.4-0.5W of light per square inch of screen. A 75g reef needs ~75 sq inches (about 8x10 inches of screen) and 30-40W of LED.
Building the chamber
Use a 1-gallon plastic container or fabbed acrylic box. Mount a roughened plastic screen (acrylic mesh from Lowes works) vertically. Pump water over the top so it sheets down both sides. Output drains back to sump.
Lighting
Red + blue LEDs (660nm + 450nm) drive turf algae growth fastest. Brands: Santa Monica Filtration Drop ATS series ($150 fully built) or DIY with 30W LED chip + driver ($25). 12-18 hour photoperiod.
Initial maturity
4-6 weeks for first algae growth. Brown diatoms first, then green turf. Don't harvest the first 2-3 weeks - let the algae establish.
Weekly maintenance
Once established: 1) remove screen, 2) scrape with razor blade or stiff brush over a bucket, 3) rinse + return. Alternate every other week if you have 2 screens. Skip a harvest week if nitrate is creeping up - the algae needs more time.
When to use vs skip
Use ATS: if you hate replacing GFO every 4 weeks, want to avoid carbon dosing, run a SPS-dominant tank with stable bioload. Skip ATS: if your tank already has chaeto refugium working well, or if light + space in sump is tight.
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