The simplest Nitrate NO₃ Recipe

DIY fertilizer with nitrate for planted aquariums

This article is dedicated to the simplest liquid fertilizer recipe containing nitrate. Nitrate is one of the key elements that planted aquarium enthusiasts pay attention to, since plants use it in large quantities compared to other elements.

I will try to explain the basic principles of creating DIY nitrate fertilizer so that any aquarist, even without special knowledge in chemistry, can make it independently.

My goal is not only to provide a nitrate fertilizer recipe for aquariums, but also to share the understanding that a recipe is not an unchangeable rule that must be strictly followed. It's just a starting point! If you change the nitrate concentration in this recipe, it won't spoil it, but rather help you select the dosage for your own aquarium.

For those who are just beginning to explore this topic, and for those who don't have deep knowledge in chemistry, I'll try to explain what concentration is using simple terms.

Concentration affects the portion of fertilizer that you will add to your tank. This portion is called dosage or dose. When talking about dosages, it's usually several ml per day or several dozen ml per week.

If your tank is small but the fertilizer is highly concentrated, you'll need to add it in very small doses, using an insulin syringe or pipette, especially if you add fertilizer on daily based approach. Having prepared a liter of such fertilizer and using only 1 ml per day, you'll face the problem of it spoiling before it's completely used, since the fertilizer is likely prepared without adding strong preservatives. As a result, after 2-3 months, mold or white fungus may appear in the container.

In the opposite situation, if the tank is large and the fertilizer is diluted (has low concentration), you'll need to add large amounts of fertilizer and frequently prepare new portions. A liter of fertilizer will be finished in several weeks, and you'll have to prepare a new batch again, which can be annoying.

To supplement the definition of concentration, it's worth mentioning that it's measured in grams per liter (g/L) for fertilizer and in milligrams per liter (mg/L or ppm) for aquarium water. For example, by dissolving 100 grams of sugar in one liter of water, you'll get a solution with a sugar concentration of 100 g/L. Thus, fertilizer can also be called an solution, since you dissolved the reagent in water.

Let's get to business. The recipe that became classic is presented as follows:

It's unknown what the original logic behind creating this fertilizer was, but apparently the recipe was developed so that 1 ml of solution would increase the nitrate level by 0.5 ppm in a 100-liter aquarium. This is quite a convenient dosing method. However, if your aquarium volume differs, for example, it's 72 liters, you'll need a dosage of 0.72 ml to achieve a nitrate level increase of 0.5 ppm. Working with such non-standard numbers and adding such fractional volumes can be inconvenient.

Note that if you decide to change the original recipe by dissolving only half the specified amount (41.44 g), the effect of the fertilizer will remain the same as when using the original concentration. The only difference is that 1 ml of solution will increase the nitrate level in the aquarium by 0.25 ppm instead of 0.5 ppm. This allows you to adapt the fertilizer concentration to your specific aquarium needs and simplifies using the solution before it spoils.

To adjust the recipe to your needs, simply use the form below. You just need to enter the tank volume, desired fertilizer volume, and appropriate dosage. That's it!

Let's assume you have a 60-liter tank, which is quite a common size. Enter this volume in the first field labeled "Tank Volume". It's important to note that the presence of carbon dioxide (CO₂) in the aquarium is critically important. Aquariums with CO₂ and without it are two completely different worlds when it comes to plants. I won't consider adding fertilizers to aquariums without CO₂, as in most cases I consider this impractical.

As a starting point for nitrate dosage, you can take 1 ppm per day or 7 ppm per week, which is usually recommended by fertilizer manufacturers. Such dosage allows you to avoid both overdosing (provided regular water changes of at least 30%) and significant fertilizer deficiency, especially if there are inhabitants in the aquarium that you feed.

As mentioned earlier, homemade fertilizer without preservatives usually lasts about three months, especially if stored in the refrigerator. If you select a dosage of 0.5 ppm in the form, you'll need to add 2 ml of fertilizer daily to ensure a total daily addition of 1 ppm nitrate. Thus, over three months (90 days) you'll need 180 ml of fertilizer. I recommend making a small reserve since components are usually inexpensive, and you won't regret throwing away excess spoiled fertilizer. Let's say you decided to use 250 ml of fertilizer. Enter this value in the second field. You don't need to enter anything else - the calculator will automatically calculate the required amount of reagent, which in your case will be 12.3 g.

Your individual recipe will be displayed in the green rectangle. You can take a screenshot, copy the text to a notepad on your computer, or write it on masking tape and stick it on the fertilizer container.

You can experiment with concentrations and volumes to find a recipe that will be most convenient for you. However, there's a limitation: the maximum solubility of potassium nitrate is 316 grams per liter. This problem may occur for aquarists with very large aquariums. For example, if you choose an aquarium volume of 400 liters and select a concentration of 0.5 ppm, a red warning about reaching maximum solubility will appear in the last field. This means that not all the reagent will be able to dissolve, and part of it may settle at the bottom. In such a situation, it's recommended to choose a lower dosage, for example, 0.25 ppm, or manually enter another, smaller value in the third field.

Congratulations! It's hard to believe at first, but you've created your own recipe that works exactly like the famous recipe, only it's also convenient specifically for you!

Good work 👍 All that's left is to prepare this recipe.

You can find the recipe for DIY phosphorus-containing fertilizer here.