How to Increase Nitrates Saltwater Aquarium Guide: For SPS

Modern reefers are almost always taught to chase nitrate down, but ultra-low nitrate starves corals and bleaches SPS pale. This how to increase nitrates saltwater aquarium guide from Gensou Aquascaping at 5 Everton Park explains when, why and how to nudge nitrate up — safely and measurably — for healthier SPS and LPS colonies. Two decades of dialling nutrient levels for SG reef clients show that 2-10 ppm is the sweet spot, and chasing zero is how corals lose colour first and tissue second.

Why SPS Need Nitrate

Stony corals host zooxanthellae that rely on nitrogen and phosphorus for photosynthesis. Strip nitrate to zero and zooxanthellae populations drop, tissue pales, polyps shrink and growth stalls. Nitrate below 1 ppm combined with phosphate below 0.02 ppm — common in heavily-skimmed tanks running carbon dosing — is the textbook recipe for bleaching. Target 2-10 ppm nitrate paired with 0.03-0.08 ppm phosphate.

Confirm the Reading First

Salifert and Red Sea nitrate kits (SGD 35-50 locally) are fine for screening but struggle below 2 ppm. If you suspect zero nitrate, send a sample to a local ICP service or use a Hanna Checker HI781 (SGD 150) for more sensitive measurement. Check the phosphate reading at the same time — they rarely drift in isolation. A reading of undetectable nitrate and 0.01 ppm phosphate is your confirmation.

Feed More, Feed Smarter

The first and cheapest intervention is food. Add a second daily feeding of frozen mysis or PE Mysis (SGD 9-12 a blister pack at Iwarna or Pinnacle). Target fish to the point where they refuse — you are not overfeeding if the fish are consuming it. Add a weekly coral-targeted feeding of Reef Roids, Polyplab Reef Roids or Fauna Marin LPS Pellets. Expect nitrate to rise 1-3 ppm over two weeks on a moderately stocked 90-gallon.

Dose Potassium Nitrate Directly

For precise control, dose laboratory-grade potassium nitrate (KNO3). A measured 75 g KNO3 dissolved in 1 L of RODI gives roughly 46 ppm nitrate concentrate. Start small — 1 mL per 100 L of tank raises nitrate roughly 0.5 ppm. Dose after lights-out and retest 24 hours later. Ramp weekly. Singapore sourcing: Chemworld and Kuala Lumpur-based online stores ship KNO3 at SGD 15-20/kg; lasts years on a nano.

Pull Back the Skimmer

An aggressive skimmer strips dissolved organics that feed the nitrate cycle. Raise the collection cup a few millimetres so the skimmer pulls wetter, more dilute skimmate. Run the skimmer eight hours overnight instead of 24 hours if your fish load is moderate. On a 30-gallon nano, this change alone bumps nitrate by 1-3 ppm within a fortnight. Reinstate full 24-hour skimming when levels stabilise in range.

Reduce Carbon Dosing

Vodka, vinegar, NoPoX and biopellet methods drive nitrate down by feeding bacteria that outcompete algae for nutrients. If you dose any of these, halve the daily volume and retest in 10 days. Stop dosing entirely for two weeks if nitrate sits below 1 ppm. Bacterial populations respond slowly, so do not yo-yo the dosing. Reef Energy AB+ at reduced frequency (twice weekly instead of daily) is often the cleanest throttle.

Remove GFO Temporarily

Granular ferric oxide (GFO, SGD 25/kg locally) strips phosphate and indirectly limits coral nitrogen uptake by creating a phosphorus deficit. If both nitrate and phosphate are rock bottom, remove the GFO reactor for two to four weeks while you rebuild levels. Reintroduce a small charge of fresh GFO once phosphate reaches 0.05-0.1 ppm if it overshoots.

Consider a Refugium Reverse Light Cycle

Chaetomorpha in a refugium consumes nitrate constantly. If levels are already too low, trim the chaeto aggressively or remove half the mass. Shorten the refugium light cycle from 12 hours to 6 hours. Local Singapore reefers often swap surplus chaeto for SGD 10-15 a fist-sized clump on Carousell — easy to rebuild if you overshoot trimming.

Monitor Response Carefully

Test nitrate and phosphate twice weekly during adjustment. A safe rise is 1-3 ppm nitrate a week. If nitrate jumps above 15 ppm, stop additions, resume a normal water change, and let it settle. Watch the corals — SPS polyp extension and colour depth typically improve within two to three weeks of hitting 5 ppm nitrate. LPS flesh plumps up faster, often in days.

Balance Nitrate with Phosphate

Nitrate alone rarely fixes pale corals. The N:P ratio matters — aim for roughly 100:1 by mass (so 5 ppm nitrate pairs with 0.05 ppm phosphate). If phosphate lags, feed coral-targeted foods richer in phosphorus, or dose Brightwell NeoPhos. A thoughtful how to increase nitrates saltwater aquarium guide approach treats nitrate as one lever in a balanced system — never a solo target — and SG reefers who get both nutrients right see the deepest colours.

Related Reading

• Reef Tank Parameters Beginner Guide
• Reef Tank Maintenance Schedule Guide
• Reef Tank Water Change Complete Guide
• Saltwater Aquarium Plants Guide
• Saltwater Aquarium Beginner Complete Guide