Testing & Water Chemistry Guide: Understanding What to Test, When to Test, and What Stable Actually Means

Section 1: What to Test (and Why It Matters)

Goal: Focus on core parameters that directly affect coral and fish health.

• *Salinity: most important baseline in a saltwater tank. Target 1.025 to 1.026 specific gravity. Too low stresses corals, too high can dehydrate tissue.
• *Temperature: target 77 to 80 degrees Fahrenheit. Large swings drive stress, bacterial blooms, and disease risk.
• *Ammonia: should remain 0 after cycling. Any detectable amount is dangerous.
• *Nitrite: should remain 0 after cycling. Spikes often point to bacterial imbalance.
• *Nitrate: target 5 to 15 ppm for many beginner corals. Too low can pale corals, too high can fuel algae and stress LPS.
• *Alkalinity (dKH): key chemistry driver for growth and pH stability. Target 8 to 9 dKH.
• *Calcium: target 400 to 450 ppm. Corals use this to build skeletons.
• *Magnesium: target 1250 to 1400 ppm. Helps stabilize calcium and alkalinity balance.

Section 2: When to Test (Simple Schedule)

Goal: Use a schedule you can actually sustain every week.

1. During the cycle (weeks 1 to 6): test ammonia, nitrite, and nitrate every 2 to 3 days. Check salinity and temperature weekly.
2. After the cycle (months 1 to 3): test salinity, temperature, nitrate, and alkalinity weekly. Test calcium and magnesium every 2 weeks.
3. Established tank (month 3 and beyond): test alkalinity and nitrate weekly. Test calcium and magnesium monthly.
4. Daily glance check: verify temperature and salinity trends, especially if using ATO.
5. If anything looks off: test alkalinity first, then nitrate, then salinity. These three explain most coral behavior issues.

Section 3: How to Read Results (Beginner Interpretation)

Goal: Interpret numbers clearly without reacting to every tiny change.

• *Salinity: rising usually means evaporation is outpacing top-off. Dropping often means too much freshwater was added.
• *Temperature: swings greater than 1 degree Fahrenheit per day can stress livestock. Improve heater reliability and room stability.
• *Ammonia or nitrite detected: pause livestock additions, retest in 24 hours, and check for dead cleanup crew or uneaten food.
• *Nitrate guide: 0 ppm may lead to pale or shrinking corals. 5 to 15 ppm is often ideal for softies, zoas, and many LPS. 20 to 40 ppm can be workable with algae monitoring. 50+ ppm usually means water-change intervention time.
• *Alkalinity: gradual drop can be normal coral consumption. Wide swings often mean inconsistent dosing or mismatch in water-change chemistry. Over 10 dKH can increase burned-tip risk on sensitive LPS and SPS.
• *Calcium: low calcium plus low alkalinity often slows growth. High calcium with low magnesium can lead to precipitation issues.
• *Magnesium: low magnesium can destabilize alkalinity. Elevated magnesium is usually less urgent than low magnesium.

Section 4: What Stable Actually Means

Goal: Redefine stability as predictable control, not perfection.