For serious reef keepers—especially those maintaining SPS-dominant systems—achieving and maintaining ultra-low nutrient levels (ULNS) is essential. In a ULNS environment, nitrate (NO₃⁻) and phosphate (PO₄³⁻) are kept at near-undetectable levels, encouraging vibrant coral coloration, tight polyp extension, and robust skeletal growth. But getting there requires more than water changes alone.
Red Sea’s range of high-performance filtration equipment is engineered to simplify the journey toward ULNS while preserving system stability. In this guide, we’ll show you how to build a complete filtration setup using Red Sea’s ReefMat, protein skimmers, filter media, and integrated app control.
Why Target Ultra-Low Nutrient Levels?
ULNS isn’t about removing all nutrients—corals still require trace amounts of nitrate and phosphate to survive. But in high-nutrient systems, unwanted algae, cyanobacteria, and brown film can smother coral and reduce light penetration.
Target nutrient levels for ULNS:
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Nitrate (NO₃⁻): 0.25 – 1.0 ppm
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Phosphate (PO₄³⁻): 0.02 – 0.05 ppm
At these levels, coral growth and coloration are optimized, especially for Acropora and other demanding SPS corals.
1. Use the Red Sea ReefMat for Continuous Mechanical Filtration
The Red Sea ReefMat is an automatic fleece filter that traps fine particulate matter, uneaten food, and detritus before it can break down into nitrate and phosphate. It features:
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Self-advancing fleece roll controlled via the ReefBeat app
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Drop-in sump design with quick-release parts
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Minimal manual maintenance
With the ReefMat, waste is physically exported from your system, not just broken down—an essential step in reducing nutrient buildup.
2. Combine with a High-Performance REEFER™ Protein Skimmer
Red Sea’s REEFER™ skimmers help remove dissolved organic compounds (DOCs) from the water column. Efficient skimming:
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Reduces protein buildup
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Improves oxygenation
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Lowers phosphate sources indirectly
Choose your skimmer size based on tank volume and bio-load. For ULNS goals, opt for a slightly oversized skimmer to handle heavy export.
3. Run Phosphate and Carbon Media in a Reactor
Pair mechanical and protein filtration with chemical media to lock down nutrient traces:
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Phosphate Remover (e.g. Red Sea PO₄x4 or GFO) binds free phosphate
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Activated Carbon removes organics and yellowing compounds
Use Red Sea’s media reactors for even flow distribution and easier maintenance. Replace media regularly based on your phosphate readings.
4. Automate and Track via ReefBeat App
Red Sea’s ReefBeat app connects your ReefMat and other equipment (like ReefLEDs and ReefWave pumps). You can:
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Monitor fleece usage
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Schedule roll advancement
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Set alerts for blockages or roll exhaustion
Automation ensures filtration consistency and reduces manual errors that can cause nutrient spikes.
5. Monitor Nutrients and Adjust Feeding Carefully
Red Sea offers Pro Test Kits for precise nitrate and phosphate readings. In ULNS systems:
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Dose amino acids and coral food cautiously (e.g. Coral Nutrition A & B)
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Adjust feeding schedules to match coral response
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Consider dosing trace elements (Coral Colors A–D) if using GFO or activated carbon
Fine-tuning input and export is the key to keeping nutrients in balance.
Bonus Tip: Clean and Maintain Filters Regularly
Even with advanced automation, regular maintenance is essential. Clean skimmer cups weekly, inspect the fleece roll, and monitor for clogs or overflow. A well-maintained filtration system is far more efficient and consistent in maintaining low nutrient levels.
Conclusion
Red Sea makes achieving ULNS more accessible with its intelligent, modular filtration equipment. By combining mechanical, biological, and chemical filtration with real-time control via ReefBeat, you can maintain a thriving reef with pristine water and radiant coral health.
