Corals are sensitive to changes in water chemistry. Stable, balanced parameters create an environment where they can grow, color up, and thrive. Poor water quality leads to stunted growth, receding tissue, and algae outbreaks.
Testing your water consistently—and understanding what those numbers mean—is essential.
Parameter | Ideal Range | Why It Matters |
|---|---|---|
Alkalinity (dKH) | 8–11 dKH | Buffers pH and supports coral skeleton formation |
Calcium (Ca) | 400–450 ppm | Needed for coral growth and LPS polyp health |
Magnesium (Mg) | 1250–1350 ppm | Stabilizes Ca and Alk levels |
Nitrate (NO₃) | 1–10 ppm | Corals need trace nutrients; too high causes algae |
Phosphate (PO₄) | 0.01–0.10 ppm | Fuel for photosynthesis, but can lead to blooms |
Salinity | 1.025–1.026 sg (35 ppt) | Maintains osmotic balance for all reef life |
Temperature | 76–78°F | Stability is more important than the exact number |
Recommended Test Kits & Equipment:
Hanna Checkers (Alk, Phosphate, Nitrate)
Salifert (Calcium, Magnesium)
Refractometer (Salinity)
Digital thermometer or Inkbird controller (Temperature)
Test | Frequency |
|---|---|
Alkalinity | 2–3x per week |
Calcium | 1–2x per week |
Magnesium | Weekly |
Nitrate/Phosphate | Weekly |
Salinity & Temp | Daily (via controller or manual check) |
Alkalinity too low? → Dose sodium bicarbonate or use an all-in-one reef buffer
Calcium drop? → Use calcium chloride (liquid or powder)
Magnesium low? → Add magnesium sulfate/chloride mix
Nitrate too high? → Water change or carbon dosing (like NOPOX)
Phosphate spike? → Use GFO or phosphate removers
🧠 Always dose slowly and test again before making large corrections.
Use a dosing pump (e.g. Jebao, Neptune DOS) for Alk, Ca, Mg
Keep logs of your test results weekly
Do regular 10–20% water changes
Don’t chase perfection—consistency is more important than exact numbers
Testing your reef tank may feel intimidating at first, but it’s one of the most important habits in reef keeping. Start small, stay consistent, and adjust your care routines based on what your tank is telling you.
Healthy water = colorful, fast-growing corals.
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