reefcalcs

Calculator

Reef Health Dashboard

Eight parameters, three bands per parameter, one screen. Drop your latest test numbers in and the dashboard tells you which are fine, which are drifting, and which need attention now. Yellow means watch and correct slowly. Red means you have a problem and the linked calculator will route you to the dose math that fixes it.

Reef Health Dashboard

Alkalinity8 dKHIn range.
Calcium420 ppmIn range.
Magnesium1350 ppmIn range.
Salinity35 pptIn range.
pH8.1 In range.
Nitrate (NO₃)5 ppmIn range.
Phosphate (PO₄)0.05 ppmIn range.
Temperature78 °FIn range.

Green/yellow/red bands track Randy Holmes-Farley's optimal-parameters consensus. Move toward the middle of the green band over days, not minutes.

How this is calculated

Green / yellow / red bands sit on a consensus of Randy Holmes-Farley's optimal-parameters guide and the Triton "method" reference values:

  • Alkalinity: green 7–11 dKH, yellow 6–7 or 11–12, red <6 or >12
  • Calcium: green 380–450 ppm, yellow 350–380 or 450–500, red <350 or >500
  • Magnesium: green 1,250–1,400 ppm, yellow 1,150–1,250 or 1,400–1,500, red <1,150 or >1,500
  • Salinity: green 34–36 ppt, yellow 33–34 or 36–37, red <33 or >37
  • pH: green 7.9–8.4, yellow 7.7–7.9 or 8.4–8.6, red <7.7 or >8.6
  • Nitrate: green 2–10 ppm, yellow 0.5–2 or 10–25, red <0.5 or >25
  • Phosphate: green 0.02–0.10 ppm, yellow 0.005–0.02 or 0.10–0.25, red <0.005 or >0.25
  • Temperature: green 76–81 °F, yellow 74–76 or 81–83, red <74 or >83

These are conservative bands for mixed reefs. SPS-dominated tanks tighten further (alk 7.5–9, NO₃ 1–5, PO₄ 0.02–0.05). Soft-coral / LPS systems are forgiving — they don't crash at 12 dKH or 0.25 PO₄, but they don't thrive either.

FAQ

Is 'green = perfect'?
Green means within the safe range and unlikely to cause acute problems. Coral health depends on stability inside that band, not on hitting a specific midpoint. A tank that holds 8.0 dKH ±0.2 for a year is healthier than one that bounces between 7 and 10 dKH every week.
What if everything is red?
Fix salinity and temperature first — those are environmental, not chemical, and livestock survive everything else better when those two are stable. Then work alkalinity in 1 dKH/day steps, then calcium, then magnesium. Address nitrate/phosphate last, slowly, over weeks — fast nutrient drops crash bacteria and trigger dinoflagellate blooms.
Why is nitrate green at 2–10 ppm, not zero?
Zero-nutrient tanks starve corals (especially LPS and softies). The 'ultra-low-nutrient' fashion of 2010-era SPS care drove a lot of tank crashes from dinoflagellate outbreaks once natural sinks (food, fish poo) couldn't keep nitrate measurable. Aim for measurable but low.
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Sources & references

  1. 01
    Randy Holmes-Farley — Optimal Parameters for a Coral Reef Aquarium (Reef2Reef thread)
    https://www.reef2reef.com/threads/optimal-parameters-for-a-coral-reef-aquarium-by-randy-holmes-farley.173563/
  2. 02
    Triton — Method reference values
    https://www.triton.de/en/the-triton-method/
  3. 03
    Randy Holmes-Farley — Magnesium in Reef Aquaria
    https://reefs.com/magazine/aquarium-chemistry-magnesium-in-reef-aquaria/

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