Aquarium water testing requires accuracy + repeatability. Freshwater starter: API Freshwater Master Test Kit ($25-30) covers ammonia, nitrite, nitrate, high+low pH. Test strips lie - skip them. Saltwater reef essentials: Salifert (alkalinity, calcium, magnesium, nitrate, phosphate) - hobby gold standard. $15-25 per parameter. Hanna Checkers (alkalinity + phosphate ULR + nitrate) - colorimeter precision in $50-90 device. Replaceable reagent packs. Trace + advanced: ICP-MS testing (Triton, ATI, Fauna Marin) ships water samples for full elemental analysis - $25-45 per test, run quarterly on reef tanks. What NOT to use: dip strips for anything beyond "is something wrong" - they're ±25% accurate at best. Old reagents (kits expire 2-3 years from manufacture). Cheap pH probes without calibration solutions. Frequency: new tanks = test every 2-3 days during cycling. Established freshwater = monthly. Established reef = weekly alk/Ca/Mg, monthly NO3/PO4. Logging: keep a parameter log so you can correlate problems with parameter shifts.
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