Reef Tank Water Parameters Explained
These are the conditions every coral we sell is grown in. The closer your tank sits to them, and the steadier it stays, the easier any new coral will settle.
| Temperature | 24 to 26°C. Keep it steady day and night with a heater and a thermostat you trust. |
|---|---|
| Salinity | 1.025 specific gravity (about 35 ppt). Top up evaporation with fresh RO water, not salt water. |
| Alkalinity | 8 to 9 dKH. The one to watch: swings here stress corals faster than anything else. |
| Calcium | 420 to 440 ppm. Builds the skeletons of LPS and SPS corals. |
| Magnesium | 1300 to 1400 ppm. Helps keep calcium and alkalinity stable. |
| Nitrate | 5 to 20 ppm. Not zero: corals need some for colour and growth. |
| Phosphate | 0.03 to 0.08 ppm. Also not zero. Bottoming it out can bleach corals. |
| Ammonia and nitrite | 0. Both must read zero before any coral goes in. |
| pH | 8.0 to 8.4. Some daily drift is normal and nothing to chase. |
Stability beats perfection
A tank held steadily at 7.5 dKH will do better than one swinging between 7 and 11 while you chase the "right" number. Change one thing at a time, and give it a week before you change anything else.
How often to test
- New tank: ammonia, nitrite and nitrate every few days until it has cycled.
- Soft corals only: salinity and alkalinity weekly is usually plenty.
- LPS and SPS: alkalinity a few times a week, calcium and magnesium weekly, as they use these up as they grow.