Maintaining a healthy reef tank starts with understanding what’s happening in your water. Regular water testing is the foundation of coral health and stability. If you’re new to reefkeeping, this guide will help you understand which parameters matter most, how to test them, and how often to test.
Corals depend on clean, stable water. Poor water quality leads to stress, disease, algae blooms, and coral death. Regular testing helps catch issues early, making your reef more resilient.
| Coral Type | PAR Range | Flow Type | Placement |
|---|---|---|---|
| SPS | 250–400 | Strong | Top |
| LPS | 75–150 | Moderate | Middle |
Parameter | Ideal Range | Why It Matters | Test Frequency |
|---|---|---|---|
Salinity | 1.025–1.026 SG | Corals rely on stable salinity | Weekly |
Temperature | 76–78°F | Fluctuations can shock corals | Daily (digital) |
pH | 8.1–8.4 | Impacts coral calcification | 2x/week |
Alkalinity (dKH) | 8–12 dKH | Essential for coral skeleton growth | 2–3x/week |
Calcium | 400–450 ppm | Key element for coral building | 1–2x/week |
Magnesium | 1250–1350 ppm | Balances calcium and alkalinity | Weekly |
Nitrate (NO3) | 2–10 ppm | Too high = algae; too low = starvation | Weekly |
Phosphate (PO4) | 0.01–0.05 ppm | High levels = algae overgrowth | Weekly |
Ammonia/Nitrite | 0 ppm | Toxic to all reef life | Weekly (cycling) |
Liquid Test Kits (e.g., Salifert, Red Sea): High accuracy, ideal for beginners.
Digital Meters (e.g., Hanna Checkers): User-friendly and fast.
Strips (not recommended): Less reliable for reef-level accuracy.
Pro Tip: Label your test tools and store them away from light and moisture.
Sudden drop in alkalinity or calcium? Dose supplements or water change.
High nitrates or phosphates? Reduce feeding, improve filtration.
Ammonia detected? Stop adding livestock; perform emergency water change.
Use a reef log to track test results over time and spot trends early.
Refractometer (for salinity)
Digital thermometer
Auto top-off unit (to keep salinity stable)
Dosing pumps (for calcium, alkalinity, magnesium)
Aquarium controller (optional, for automation)
Test at the same time of day for consistency.
Don’t chase perfection—stability is more important than exact numbers.
Record your tests weekly in a notebook or app.
Always double-check unusual results.
Understanding your water chemistry is one of the most empowering steps in reefkeeping. With regular testing, you’ll gain insight into your reef’s behavior, allowing you to correct issues before they become problems. It’s not just about numbers—it’s about keeping your reef thriving.
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Dream World Corals is a trusted online coral retailer specializing in hand-selected, ethically grown WYSIWYG corals. With an unwavering commitment to reef health, we provide hobbyists of all levels with premium corals backed by expert care, safe shipping, and our industry-leading 72-hour live arrival guarantee. Our mission is simple: help your reef thrive.
