Fertilizing aquarium plants isn’t as straightforward as it might seem. Unlike regular plants, there have very specific requirements.

For that reason, we always advise our readers to go for liquid fertilizer rather than tabs or other forms of fertilizer.

In this article, we’ll guide you through our 5 favourite liquid fertilizers for aquarium plants and their composition and pros and cons.

The ideal NPK Ratio for Aquarium Plants

 

NPK stands for Nitrogen, Phosphorus, Potassium (respectively). Whilst simply giving each of these nutrients is important, the ratio in which these are given is also of great importance.

The ideal NPK ratio is a bit of a myth, as different plants have different requirements, but there are some general guidelines that you can follow to successfully and quickly grow plants in water.

These requirements vary not only with the genetic composition of the plant, but also the condition of the water, soil, etc, so before we recommend macro and nutrient ratios, we advise you to consult one of the many online forums on the subject, and/or the handy image below:

Ideal NPK Ratio for Aquarium Plants

Having said, that, if your plant doesn’t appear to show any signs of nutrient deficiency but you still want to feed it some nutrients, here are some important rules of thumb:

  • Water plants need much more nitrogen and potassium than phosphorous, thus you should look for ratios that are heavy in the N and K. Example: 10:1:10
  • If you want to go deeper, there are frameworks for calculating ideal ratios, we recommend checking out the Estimative Index (EI) method. You can read more here.

 

A word of caution: Using “normal” terrestrial fertilizer on aquarium plants is risky business as the Nitrogen usually comes in the form of urea, which breaks down to ammonia, which is something you don’t want hanging around your water.

Our #1 Choice: Thrive Liquid Fertilizer for Aquarium Plants

Ok, we’ll admit that this isn’t the cheapest fertilizer in the market.

However, it is highly concentrated and in our experience can last for up to 1 year.

Per 10 gram serving, your plants will get 7ppm NO3, 1.3ppm PO4, 5ppm K, and 0.25ppm Fe.

It’s NPKratio is 3:08:9.4 and it also has 0.47% fe.


Our budget choice: API Leaf Zone Fertilizer

If you’re a beginner this really is all you need.

With a ratio of 0-0-3, this fertilizer focuses on Potassium, an essential nutrient for any water plant. It also offers 0.1% of iron, covering all the basic nutrients your plant needs to thrive.

Unless you’re planting a very exotic/specific type of plants, this is the fertilizer we recommend using without thought. Simply give your plant 5 ml per 10 gallons of water once a week and you’re good to go.


Note: According to feedback received, this fertilizer won’t harm any fish you have in your aquaria, but worms might die. Keep that in mind if you intend to purchase this product.

Other recommended fertilizers:


 

Final Thoughts

And there you have it. We hope this guide has helped you purchase your liquid fertiliser for your aquarium plants, and as always, if you have any feedback, please let it in the comment box below!