How to Add Potassium Nitrate to an Aquarium

Potassium nitrate is a fertilizer that is frequently used to feed aquarium plants. The Planted Tank website recommends dosing plants with fertilizers and nutrients separately rather than using a single chemical that claims to provide all nutrients. This ensures that plants get the proper dose of potassium nitrate. Generally speaking, most aquarium plants require 5 to 10 parts per million of potassium nitrate.

  1. Potassium Nitrate Benefits

    • Plants require both potassium and nitrate to properly photosynthesize light, according to the textbook "Biology: Life on Earth with Physiology." While small quantities of these nutrients are available in most tanks, it is difficult to obtain a proper nutrient balance -- particularly in small indoor tanks -- without adding nutrients. Before adding any fertilizers, use pH testing strips to test your aquarium for nutrients. Many aquarium stores can perform free tests on water samples to determine nutrient balances.

    Potassium Nitrate Quantities

    • Different plant species require different quantities of potassium nitrate, so check the care instructions for the plants you have chosen. On average, plants require 5 to 10 parts per million of potassium nitrate. A quarter teaspoon, or 1.4 grams, of potassium nitrate will increase the parts per million of potassium nitrate by 4.5 in a 50 gallon tank, according to the book "Freshwater Aquarium Chemistry."

    Adding Potassium Nitrate

    • Add 40 grams of potassium nitrate powder to 500 ml of distilled water. Allow the powder to dissolve in the water and then shake the solution to ensure an even consistency. Then add 5 ml of the solution for every 50 gallons of aquarium water. Pour the solution directly into the aquarium. If you notice clouding, stop adding solution.

    Tips and Warnings

    • Potassium nitrate can burn the skin and eyes, so wear gloves when using it and never inhale it. While small quantities are safe for fish, using large quantities of fertilizer in a tank is unsafe, so never exceed the recommended label dosage. To encourage plant growth, provide a full spectrum UVA/UVB bulb in the tank.