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What is the best fertlizer for a planted tank?

Updated: Feb 2

If you are more of a visual learning, than a reader, we made a video you can watch about this topic. Check it out here:

If you learn better from reading, well you're not going to want to miss this article. AND for those that don't want to learn, go out and buy this stuff. Dose the full dose if you are running CO2, and half the dose if you're not.

For those that WANT to learn, we need to first talk about what fertilization a plant needs. There are two major groups of nutrients, Macro and Micronutrients.

Macronutrients consist of:

  • Nitrogen (N)

  • Phosphorous (P)

  • Potassium (K)

Micronutrients consist of:

  • Iron (Fe)

  • Manganese (Mn)

  • Chlorine (Cl)

  • Copper (Cu)

  • Boron (B)

  • Molybdenum (Mo)

  • Cobalt (Co)

  • Nickel (Ni)

  • Magnesium(Mg)

  • Calcium(Ca)

  • Sulfur(S)

  • Zinc(Zn)

The best fertilizers are the ones that include all of the Macro AND Micro nutreints. With that understanding, there are a lot of companies that just pick random nutrients, like API, and they toss those into a bottle with lots of water. For example, API Leaf Zone. I see hobbyists asking if this is a good one. It has two of the fifteen nutrients. Potassium, and Iron.

How did they come up with those two? Like, "This is enough, we'll call it good there". HAHAHA. Furthermore, Seachem wants you to buy EIGHT bottles to achieve a holistic fertilizer! That came out to $84.47 on Amazon at the time of writing this article... and there is no liquid carbon Seachem, quit calling it that.

I don't understand why companies do this. Actually, I do. They don't want to make it easy for you, they want it to be profitable for them. OK! Rant over

We really like the Estimative Index (EI) method of fertilization. This idea is based on LieBig's Law of the Minimum which states "that growth is dictated not by total resources available, but by the scarcest resource". This means that growth will be hauled if we're missing a nutrient, regardless if we have EVERYTHING else. From our perspective, you should dose ALL the nutrients so that plants don't go "I'm missing some Phosphorus, so I'm going to stop growing." and the EI method does that exactly. It provides everything, in excess, to make sure your plants never run out of a single nutrient.

So which fertilizer is closest to the EI method? There is really only one that comes to mind, and its the Thrive line up. They have a handful of options to fit your tank's needs, but their "All in One" is one of the best, hands down. It has all the above-mentioned nutrients and their Thrive+ is even more concentrated. This is as close to the EI method as you're going to get.

Here is what is in it:

  • Total Nitrogen (N) 2.5600%

  • Water Soluble Nitrogen (N) 2.5600%

  • Available Phosphate (P2O5) 1.5800%

  • Soluble Potash (K2O) 9.7400%

  • Magnesium(Mg) 0.3200%

  • Water Soluble Magnesium(Mg) 0.3200%

  • Calcium(Ca) 0.0200%

  • Sulfur(S) 0.5400%

  • Combined Sulfur(S) 0.5400%

  • Boron(B) 0.0080%

  • Copper(Cu) 0.0002%

  • Water Soluble Copper(Cu) 0.0002%

  • Iron(Fe) 0.4200%

  • Water Soluble Iron(Fe) 0.4200%