ICP Testing Explained: Is It Worth the Money?

What Is an ICP Test?

ICP (Inductively Coupled Plasma) analysis is a laboratory test that measures the elemental composition of tank water with precision home test kits can't match. A water sample goes to a lab, and a few days later a report shows levels of 30-40+ elements — calcium, magnesium, alkalinity, but also tin, copper, aluminium, and things most reefers never think about.

How It Works

Buy an ICP test kit (typically £25-40 per test)
Fill provided vials with tank water (and sometimes RODI source water)
Post it to the lab
Results come back in 3-7 days

Popular UK providers include Fauna Marin, ATI, Triton, and ICP Analysis UK.

What ICP Tests Are Good For

Catching Hidden Problems

Heavy metal contamination — copper from plumbing, zinc from cheap equipment. Even tiny amounts cause mysterious coral deaths
Trace element depletion — iodine, potassium, strontium, iron
Unusual imbalances — elevated tin from certain salt brands, aluminium from GFO batches

Validating Home Test Kits

ICP results reveal whether home test kits are reading accurately — useful for calibration.

Source Water Quality

Testing RODI water catches failing membranes, exhausted DI resin, or contamination in storage containers.

What ICP Tests Are NOT Good For

Day-to-day monitoring — it's a snapshot. By the time results arrive, parameters have moved
Quick problem diagnosis — if a coral is dying now, home test kits are needed immediately
Dosing instructions — "recommended" actions from some ICP services can be overly aggressive

When to Test

Most reefers: Every 3-4 months. Catches slow-building contamination and depletion
SPS keepers: Quarterly is close to essential. SPS corals are sensitive to trace element imbalances
Fish-only or soft coral tanks: Once or twice a year is likely sufficient
Troubleshooting: When something's wrong and the cause is unclear, an ICP test (including RODI source water) can be revelatory

Tips for Accurate Results

Test on a "normal" day — not right after a water change
Follow sample collection instructions exactly
Test RODI water at the same time for comparison
Keep results over time — trends are far more useful than a single snapshot

At £25-40 per test, it's a fraction of the cost of a dead acropora colony.