API Nitrate Freshwater And Saltwater Aquarium Test Kit

Nitrate is the end of the nitrogen cycle and the only one of the three that a working filter will not remove for you — it accumulates until a water change takes it out. This kit reads it from 0 to 160 ppm in fresh and salt water, roughly 90 tests per kit. Sustained high nitrate rarely kills outright; it shows up as fish going off their food and looking flat, and as algae that keeps coming back.

What is in the kit

• 2 test solutions
• 1 test tube with cap
• Colour chart and instruction manual
• Around 90 tests

Reading it properly

Solution 2 has to be shaken hard for the full time the booklet states, and the capped tube then inverted rather than shaken. Skipping that step is the usual reason a nitrate reading comes back lower than it should.

Looking after the kit

Rinse each tube with tap water straight after use — dried reagent stains the tube and throws out the next reading. Never wash tubes with detergent; the residue is harmful if it goes back into the tank. Shake the reagent bottles firmly, but invert the capped tube gently.

In a reef tank, test it alongside phosphate. For everything at once, see the Freshwater Master Test Kit.

API Nitrate NO3 Test Kit on the API website