Aquarium Test Kits and Water Parameters
Which water parameters to monitor and why — ammonia, nitrite, nitrate, pH, KH, GH and temperature for freshwater, plus salinity, calcium, magnesium and alkalinity for marine — and how often to test.
Testing tells you what is happening in water that looks perfectly clear. The nitrogen cycle produces ammonia and nitrite, which are toxic, so both should read zero in an established tank; nitrate is the far less toxic end product, which you keep low with water changes. Ammonia is especially dangerous because its un-ionised form (NH3) is roughly 100 times more toxic than ionised ammonium (NH4+), and that toxic fraction rises as pH and temperature go up — so the same ammonia reading is more dangerous in warm, high-pH water.
Freshwater core parameters
- Ammonia (NH3): target 0 — any reading signals a problem.
- Nitrite (NO2): target 0 — also toxic, watch it closely during cycling.
- Nitrate (NO3): the accumulating end product; keep it low by exporting with water changes.
- pH: how acidic or alkaline the water is; most species have a preferred range, and stability matters more than a specific number.
- KH (carbonate hardness / alkalinity): the water's buffering capacity — it holds pH steady, and nitrifying bacteria need alkalinity to work.
- GH (general hardness): the total calcium and magnesium content of the water.
- Temperature: check it with a reliable thermometer.
Marine and reef add-ons
| Parameter | Typical marine/reef target |
|---|---|
| Salinity / specific gravity | ~1.023–1.025 (about 35 ppt) |
| pH | ~8.1–8.4 |
| Alkalinity | ~8–12 dKH |
| Calcium | ~400–450 ppm |
| Magnesium | ~1250–1350 ppm |
| Nitrate | near 0 in reef tanks; ammonia and nitrite 0 |
Reef tanks add salinity (measured with a hydrometer or, more accurately, a refractometer), plus calcium, magnesium and alkalinity, because corals consume these to build their skeletons. On test methods, liquid reagent (titration) kits are generally regarded as more precise than dip strips, which are quick and convenient but coarser. On cadence: test frequently while a tank is cycling or brand new — several times a week to follow the ammonia-to-nitrite-to-nitrate progression — then settle to about weekly on an established tank, or whenever something looks off.
Sources: ask.ifas.ufl.edu , en.wikipedia.org , en.wikipedia.org , reefbuilders.com