From The Aquarium Wiki
Sodium nitrate (NaNO3) (also know as Nitrate of Soda) is a chemical compound used in the aquarium hobby as a nitrate addition in planted aquariums where good growth often causes the plants to consume all the nitrate produced. Usually it is Potassium nitrate that is used as that also adds the macro-nutrient potassium that plants use.
- Used as part of the PMDD fertiliser method.
- The effects of adding lots of sodium in the water is unknown at present. It is thought to be harmless as long as water changes are regularly performed to dilute it.
- Tt can be obtained in Garden centres quick cheaply as it's a common fertiliser.
- One quarter tsp or 1.8g of NaNO3 with give you a 7ppm increase of nitrate in 190L (50 US gallons) of water.