ICP (inductively coupled plasma) labs measure dozens of elements at once. They're powerful for spotting pollution (copper), depleted magnesium, or odd salinity — and easy to overreact to. Research context: ICP and trace elements guide.
What ICP is good for
- Confirming magnesium, potassium, sulfur when home kits disagree
- Detecting copper, zinc, nickel from contaminated equipment or treatments
- Checking whether RO/DI is letting silica or phosphate through
- Seeing long-term trends with tests every 2–3 months
What to take with caution
- Ultra-trace metals near the lab's detection limit
- Single-point "low iron" or "low iodine" without coral symptoms — seawater references and lab accuracy vary
- Lab-to-lab differences; stick to one reputable lab for trends
A conservative response plan
- Fix salinity, alk, Ca, Mg and nutrients first with home tests.
- If copper or other toxins are high, large water changes and remove the source; don't "dose around" pollution.
- For modestly low major ions (Mg, K), correct with known supplements and retest.
- For trace elements, prefer water changes with a quality salt over shotgun dosing, unless you have a clear deficiency pattern and a trusted product.
Sources
FAQ
How often should I ICP? Every 2–3 months for most tanks, or after major water-quality events.
Is ICP a replacement for daily alk tests? No. Alk and nutrients still need frequent home testing.