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WATER TESTING & MAINTENANCE

Nitrate Test Kit

Reads the end product of the nitrogen cycle, and the number that sets your water-change schedule.

Maintaining stage Water
Unplug before servicingHands out of the water firstDrip loop on every cableTest before you dose30 ppm CO₂ ceilingCycle before stocking
WaterTechnical line drawing of Nitrate Test Kit
Specification
MethodLiquid reduction + colour match
Range0–160 ppm (two scales)
Resolution~5 ppm at low range
Tests per kit90–180
Read time5–10 minutes
InterferenceNitrite present reads as nitrate
Technical parameters
Target, planted10–20 ppm
Acceptable ceiling40 ppm
Water-change trigger> 40 ppm
Test frequencyWeekly before water change
Shake requirement30 s bottle, 1 min tube
Zero readingPlants consuming it — normal

Nitrate is where the nitrogen cycle ends. Ammonia from fish waste and decaying matter is oxidised to nitrite, then to nitrate, and nitrate accumulates because nothing in a normal filter removes it. Water changes and fast-growing plants are the only two exports in a planted tank.

The target band is roughly 10–20 ppm. Below that, plants may be nitrogen-limited and growth stalls; above 40 ppm, algae have the advantage and long-term fish health suffers. In a heavily planted, lightly stocked tank, plants can consume enough nitrate that it reads near zero, which is not a problem — it means the plants are doing the work.

The measurement itself has a trap. Most liquid nitrate kits work by reducing nitrate to nitrite and then colour-matching, and the reagents are sensitive to how hard and how long you shake the bottle. The instructions say to shake for thirty seconds for a reason; skipping it under-reads by a factor of two or more.

Safety and welfare
  • If nitrite is also present, the nitrate reading is inflated. Always check that the cycle is complete before trusting a nitrate number.
  • A nitrate reading above 80 ppm means the maintenance routine has failed somewhere. Do two 30% changes a day apart rather than one 60% change.
  • Keep reagents sealed and out of sunlight. The reducing agent oxidises and silently reads low.

Using it well

Test before the water change, not after. The pre-change number is the one that tells you whether your schedule is working.
Log the number. A slow upward trend across three weeks is the earliest warning that bioload has outgrown your maintenance routine.
If nitrate is always zero in a heavily stocked tank, check the kit is not expired. A dead reagent and a perfect tank look identical.

Test alongside

pH test kitGH/KH test kitWater changerNitrogen cycle article
Note. Parameters are conventional ranges across the category, not the claim of any one manufacturer. Nothing on this page is for sale and no outcome for any plant or animal is guaranteed. Simulator output elsewhere on this site is a simplified model, not a measurement — confirm everything with a test kit and the equipment's own instructions.
Related

Works alongside

pH Test KitWaterGH / KH Test KitWaterWater ChangerWater