Colombo N03 Nitrate pond water test Kit.
NO3 is produced from the breakdown of nitrite in the filter.
Nitrate is relatively harmless to freshwater fish, but its presence can indicate a deterioration in the aquarium environment, and high nitrate will encourage algal growth.
The only way to know what the nitrate level is, is by testing it with a Nitrate test kit.
Colombo Nitrate Pond Test Kit contains 40 tests.
How To Use Colombo NO3 Nitrate Test Kit: