DIY Algae Scrubber Build Guide: Upflow and Waterfall Types
An algae scrubber is the single most powerful nutrient export device you can build for under $50 in Singapore, and once dialled in it outperforms most shop-bought GFO reactors. This diy algae scrubber build guide from Gensou Aquascaping at 5 Everton Park covers upflow, waterfall and bucket formats with specific lighting, flow and harvest guidelines. The catch: scrubbers grow the algae you want in a controlled chamber so your display does not have to, and they reward the patient reefer who sets one up early rather than chasing nutrient crashes later.
How Algae Scrubbers Work
A rough plastic screen under bright red-heavy light grows a mat of turf algae. Water flows across the mat; algae strip nitrate and phosphate directly, converting them to biomass. You physically remove the mat each week, exporting concentrated nutrients permanently.
Compared to chaeto refugium export, scrubbers export 2 to 3 times more nutrient per litre of reactor volume but require weekly maintenance.
Scrubber Types
Waterfall: water sheets over a vertical screen, both sides lit. Most efficient but wet-loud and splashy. Upflow: water bubbled up through a submerged screen inside a chamber, lit from outside. Quieter, fits in sumps, less efficient than waterfall. Bucket: a small submersible variant for nano tanks, grows less but easy to build.
Screen Material
Roughened plastic craft canvas (plastic needlepoint mesh) is the standard. Rough both sides with 60-grit sandpaper in circular motions until the plastic is visibly scuffed. Smooth plastic will not host algae attachment. Available at Art Friend or Spotlight for around $3 per sheet.
Lighting Specifications
Dedicated red/blue LED strips peaking at 660 nm red and 450 nm blue, 2:1 red to blue ratio. Aim for 0.5 to 1 watt per square inch of screen. A 5 by 6 inch screen needs 15 to 30 watts of high-quality LED at 2 to 3 cm distance from the screen.
Cheap Shopee red grow strips at under $15 work adequately. Kessil H80 at the premium end outperforms substantially but costs $180.
Photoperiod and Acclimation
Run lights 18 hours on, 6 hours off. Algae photosynthesis plateaus around that duration and the dark period prevents pigment breakdown. New screens need 10 to 14 days to seed; do not scrape during that window even if growth looks patchy.
Flow Requirements
Waterfall: 35 to 50 litres per hour per inch of screen width. A 15 cm wide screen wants 200 to 300 LPH from a small powerhead. Upflow: similar throughput but as flow through the chamber, bubble entrainment included. Undersized flow starves the screen and favours slimy cyano; oversized flow washes young attachment off.
Build: Simple Upflow
A 3-litre rectangular acrylic box with a lid, roughened screen suspended inside by acrylic rod hangers, a small air pump feeding a bubble stone at the base, and red/blue LEDs mounted against the clear walls. Total cost around $35 from local craft and hardware sources.
Build: Waterfall
A horizontal slot pipe (1 inch PVC with a 2 mm slit cut along 15 cm) feeds water across a vertical screen held between two acrylic sheets. Water falls into the sump directly below. Add a splash hood to prevent evaporation loss and salt creep onto nearby LED drivers.
Harvest Protocol
Week 1 to 2: leave untouched, seeding only. Week 3 onward: harvest weekly or bi-weekly. Remove the screen, scrape half the algae off with an old credit card into a bucket. Leave a thin layer for re-seeding. Rinse screen briefly in tank water (not freshwater, which kills pods), return to unit.
Reading the Mat
Dark green hairy turf: ideal, exporting well. Bright green slimy: flow too low, increase. Brown diatom dominance: light too weak or new screen still establishing. Red-black cyano: cyanobacteria outcompeting, cull mat entirely and restart seeding with stronger light.
Singapore Climate Notes
Scrubbers evaporate fast in warm sumps. A waterfall unit in a 28°C sump can add 1 to 1.5 litres of daily evaporation; size your ATO reservoir accordingly. The humidity vented into the cabinet also accelerates electrical corrosion, so install a computer fan pulling air through.
Pairing With Other Export
A well-running scrubber can replace GFO entirely and reduce skimmer load. Do not stack full-strength scrubber plus aggressive carbon dosing plus GFO; you will bottom out phosphate and the tank will dino or cyano within weeks. Start with the scrubber alone and remove other export pathways one at a time as parameters stabilise.
Related Reading
emilynakatani
Still Have Questions About Your Tank?
Drop by Gensou Aquascaping — most walk-in questions get answered in under 10 minutes by someone who has set up hundreds of tanks.
5 Everton Park #01-34B, Singapore 080005 · Open daily 11am – 8pm
