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Our approach is to supplement nutrients through fertilization. Our technique 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 of if we have all the other nutrients available. Liebig used the image of a barrel with unequal staves to explain how plant growth is limited by the nutrient in the shortest supply. Just as the level or water is limited to the shortest stave.You could be dosing all sorts of stuff, but if you’re missing something like Potassium, your plant's growth will be stunted. From this perspective, we should dose ALL the different nutrients a plant could need, so that plants don't say "I'm missing Potassium over here, I'm going to stop growing!". Hitting our plants with medium to high PAR, asking them to grow, and then not providing the nutrients to do so really stresses a plant out, and invites algae to come hang out.



We really like the Estimative Index, or the EI method of fertilization. It provides everything, in a small amount of excess, to make sure your plants never run out of a single nutrient. Awesome huh. The EI method is broken into two categories, macronutrients, and micronutrients. Macronutrients are the big elements that your plants need a lot of, and the micronutrients are just that, elements that your plants need very little or of, or as the pros say, trace amounts of. The EI method also addresses the question, how much should you dose? The macros and micros were designed within a specific ratio. If you have an aquarium without plants in it, all you need to do is dose enough fertilizer to get your nitrates up to around 20ppm, and keep them there throughout the week. Every tank is going to consume more or less fertilizer due to the aquarium’s plant mass, but just keep your nitrates around 20ppm, and you’re good! Because the EI method is locked to a set ratio, if your nitrates are where they need to be, we automatically know that the phosphates and potassium are where it needs to be as well. So there is no need to buy a bunch of fancy test kits for all the different types of nutrients… shoot, that just is too much work for us.


As discussed, are two main categories of nutrients: Macronutrients and Micronutrients. Below is what they are and how they help our plants thrive!

Macronutrients – Nutrients that our plants need a lot of.  Nutrients of special importance in our tanks is what is called “NPK”, short for Nitrogen (N), Phosphorus (P) and Potassium (K). Other macronutrients include Calcium (Ca), Magnesium (Mg) and Sulfur (S).

  • Nitrogen (N) – an essential part of all living cells; it must be present for protein synthesis. Nitrogen is an important part of chlorophyll (the green pigment in plants). Nitrogen is usually provided to plants in the form of nitrate, and is usually deficient in tap water, where it is considered a contaminant.

  • Phosphorus (P) – an essential component of photosynthesis; helps convert light into sugars that plants use to feed. Excess phosphorus without adequate light levels can contribute to algae growth. Usually present in adequate amounts in tap water and is added to the tank by the addition of fish food.

  • Potassium (K) – important in protein synthesis and helps plants to metabolize iron. Aquariums are usually deficient in it, but plants require huge amounts of potassium for growth.

Micronutrients – Also known as “trace elements” because our plants need them in really small (or trace) quantities. High quantities can be toxic to plants and livestock.

  • Boron (B) – helps the plant produce sugars and starches and is essential for the regulation of other nutrients.

  • Copper (Cu) – stimulates the production of proteins which makes it essential for plant reproduction.

  • Calcium (Ca) – a component of cell wall structure, calcium helps provide strength to the plant and helps transport other nutrients throughout the plant. Usually present in adequate quantities in most municipal water areas, where it is responsible for “hard” water.

  • Magnesium (Mg) – component of chlorophyll in plants, essential to the transport of iron in the plant. Like calcium, magnesium is likely present in adequate quantities in “hard” water areas.

  • Sulfur (S) – helps in chlorophyll production, is essential for healthy root growth and stimulates rapid plant growth. Sulfur is usually deficient in all but the hardest tap water.

  • Chloride (Cl) – plays a role in the metabolization of other nutrients. Usually present in chlorinated water (dechlorinators convert Chlorine into a salt of chloride). May be deficient in well water or deionized water.

  • Iron (Fe) – must be present to manufacture of chlorophyll and, thus, is essential for plant growth. Without adequate iron (about 0.1 to 0.5 ppm), plants will yellow and fail to produce dark green growth. Iron is usually deficient in all municipal water.

  • Manganese (Mn) – aids in the digestion of starches and nitrogen and helps the plant to use other minerals. Because of that, a deficiency in manganese may give the appearance of a deficiency in one of the other nutrients, such as iron (yellowing leaves).

  • Molybdenum (Mo) – assists the plant in metabolizing nitrogen.

  • Zinc (Zn) – is essential for carbohydrate metabolization and helps to regulate plant growth.

There are also 3 main elements that our plants need that are not mineral-based, and they are Hydrogen and Oxygen, which come from our water, and Carbon, which comes from injecting Co2 into the water and from fish respiration.  This nutrients section primarily discusses the mineral-based (macro and micro) nutrients.


There are lots of companies, like Seachem, that sell individual bottles of each Macro Nutrient (just Nitrogen, or just Phosphates, or just Potassium, etc).  But because they don’t include a comprehensive dosing schedule of all required nutrients, it can be difficult to diagnose what nutrients your plants might be lacking if they are not healthy and happy. In my perspective, you’re just going to be “throwing darts in the dark” hoping you have enough nutrients at the correct ratio. Some people also look at charts and ask, "which nutrient am I running out of". But with the understanding we have of Liebig's Law of the Minimum, they would know if they dose more of a single macronutrient, they would just run out of another stalling plant growth again. It’s also not very cost or space-efficient to buy separate bottles of every nutrient you will need for your plants. I never recommend individual bottles of nutrients, and if you wanted an all-in-one, I would suggest a comprehensive fertilizer like NilocG Thrive+ which is based of the EI method. Watch the video below for more information. 


EI Kit .png

It's really easy to start dosing the EI method, all you need is an EI kit. These are available on many websites, but the best prices we've found ar on Nilocg’s website. The kits come with a few bags of these individual fertilizers which are in salt format. Also, make sure you pick up some dosing bottles as well as they’ll make your life a lot easier. You follow a recipe (below) and add these salts into a dosing bottle with water in it, and shake! BAM, you have fertilizer. Some additional reasons we love the EI method, are:

1) These fertilizer bags will last you a LONG time. We were able to use a $35 EI kit for almost 3 years in my 28-gallon aquarium. Using an EI kit and mixing your own fertilizer is FAR more cost-effective than buying bottles of fertilizer. After all, companies are really just selling you saltwater in a bottle.

2) The nice thing about the EI method is you can customize it to your tank's needs. Let say you have a tank that is heavily stocked with fish, and your nitrates are already sitting around 20ppm. You can simply reduce the amount of nitrates you’re mixing up a batch of fertilizer,  and rely on the naturally available nitrates that your fish produce!

This is a little more of an advanced approach, but it is awesome to have this kind of customizability in your fertilization method. Though all in ones are really convenient, we obviously can achieve this level of customizability. The biggest thing we need to be aware of thought when using the EI method, is we need to process 50% water changes weekly. This ensures there is not a build-up of a single nutrient in the water column.... because like everything in the hobby, consistency and balance is key! Check out the recipe and dosing instructions below to get an idea of how easy the EI method is. 

The EI Method targets these nutrient ranges:

  • CO2 range 25-35 ppm

  • NO3 range 10-30 ppm

  • K+ range 10-30 ppm

  • PO4 range 1.0-2.0 ppm

  • Fe 0.2-0.5ppm or higher

  • GH range 1-2 degrees "extra" 17-40 ppm or higher



  • BOTTLE #1 - Macro Nutrients (500ml bottle)

    • KN03 (Potassium Nitrate) – 4 TSP / 30G

    • KH2PO4 (Mono Potassium Phosphate) – 1 TSP / 5G

    • K2S04 (Potassium Sulfate) – 6 TSP / 35G

  • BOTTLE #2 Micro Nutrients (500ml bottle)

    • CSM+B (Chelated Trace Elements) – 1 TSP


    • High light only – 10ml per 50ltr (13.2 US gal) for both Macro and Micro

    • Monday Macro

    • Tuesday Micro

    • Wednesday Macro

    • Thursday Micro

    • Friday Macro

    • Saturday Micro

    • Sunday - 50% water change


Full kits of either can be purchased here – For the EI method, make sure you get the 500ml bottles as well. Those and a syringe make dosing super easy.

Again, the EI Method targets these nutrient ranges:

  • CO2 range 25-35 ppm

  • NO3 range 10-30 ppm

  • K+ range 10-30 ppm

  • PO4 range 1.0-2.0 ppm

  • Fe 0.2-0.5ppm or higher

  • GH range 1-2 degrees "extra" 17-40 ppm or higher



Now that we have a way to keep nutrients levels consistent and in abundance, how to provide them to the plants? Well, since the EI method is dosed directly into the water column, column feeders, like epiphytes, mosses, floaters, they are going to pull it directly from the water. So we have those plants covered… but what about the root feed plants, like stems, swords and carpeting plants, things like that. This is where an aquasoil comes in. But first let’s talk about cation exchange capacity, or CEC


CEC is a measurement of substrates' ability to soak up nutrients from the water column, kinda like a sponge, making these nutrients readily available for root-feeding plants. The higher the CEC, the better it will soak up nutrients. 


For comparison’s sake, generic gravel has a CEC of 1.3. Seachem Fluorite, which is baked clay, has a CEC or around 1.7. This is REALLY low for a substrate that is marketed as a “planted tank” substrate. We also did some research on EcoComplete, which is volcanic basalt, and it has a low CEC of around 15. So many boast that it’s “packed with nutrients and had a high CEC”, but that is just not the case. Read this article that talks about a scientific study performed on volcanic basalt, outlining its low CEC and lack of nutrients.


Now, aquasoils on the other hand have a CEC of around 50! That is over 3x the absorption rate of EcoComplete which is mind-blowing. This is why we like to pair aquasoils with the EI method. It will soak up all the goodness that the EI method has to offer, keeping those root-feeding plants SUPER happy.

CEC of common Aquasoils.jpg


Only rinse a substrate if you are instrcuted by the manufacture to do so. A lot of times with aquasoils you are rinsing away nutrient that could be helping your plants. Futhermore, do not cap an aquasoil. This is misinformation that is being spread. Substrate caps are only used when using fine organic dirt, as its messy and will get all over the tank without a "cap". 


Aquasoils most closely resembles the soil at the bottom of lakes and rivers. Because of its high CEC, an aquasoil can absorb nutrients from the water column and are taken in by the roots of root-feeding plants.  Aquasoils provide the most amount of benefit for a planted tanks. aquascape.

Diane Walstad (the pioneer of low-tech tanks) talks about the importance of organic matter in our aquariums.  Aquasoils are a perfect breeding ground for a bed of bacteria that break down organic matter (i.e. fish poo and plant detritus) into a nutrient-rich humus. The humus readily bonds to hard metals that can cause metal toxicity (bonus: this process also softens water).  A byproduct of this bacterial breakdown is additional Co2, which your plants can take in.  A good example of the organic breakdown in hummus is the reduction reaction with ferric iron (FE+3) to create ferrous iron (Fe+2), which is a plant’s preferred form of iron (it is more likely to absorb it in this form).  If you aren’t interested in all the science, the take-home message here is that nutrients and bacteria in the substrate is good for our plants.  If you can’t get enough science, read this.

Aquasoils tend to buffer the water parameters down, decreasing your water's hardness, pH and KH.  They also tend to cause an initial (first 1-2 weeks) spike of ammonia (when first introduced to the tank).  This is great if you are starting a new tank as it will speed up the process of cycling your tank.  If you are converting an existing tank with live fish in it to an active substrate, just be mindful that you may need to increase water changes initially to keep the ammonia in check

The biggest downside of aquasoils is they don't last forever. Over time the nutrients they contain are absorbed by plants causing the aquasoil to breakdown, HOWEVER, if 'we're dosing a liquid fertilizer then we don't need to rely on the aquasoil nutrients. With that being said, I have tanks that I've used remineralized RODI water and does the water column using the EI method and had it last 6+ years... and it's still going strong. So I think the less you rely on the aquasoil to buffer your water and fertilize your plants, the longer it lasts. They are delicate though which means we generally don’t want to mix them with other harder substrates as it can grind down the substrate as you plant and replant over time. The nice part about the aquasoil having a high CEC, is when you dose fertilizers into the water column, the substrate will soak that nutrient up like a sponge and provide it to the plant's roots.  

Good examples of active substrates are Fluval Stratum, ADA Amazonia and Tropica's Aquarium Soil. Some even use, specifically, “Miracle Grow’s Organic Potting Soil”. It can yield great results, however, it is really messy in a tank and for that reason, I do not recommend it.


Thanks to what we’ve learned from Liebig's Law of the minimum, we just need to provide all the different macros and micros in excess, to make sure our plants don’t run out of anything at any time. We achieve this by running the EI method, or buying an all-in-one based off the EI method, like Thrive, TNC Complete, APT EI, or LCA All in One.. depending on where you live. The EI method not only feeds the plants in the water column, but when paired with a high CEC substrate, like an aquasoil, the aquasoil will absorb the nutrient making it readily available for root feeding plants. This way everyone in the tank is happy at all times. Also, if you have chosen to not run CO2, you will dose the same way by keeping your nitrates at 20ppm. You’ll just end up needing less nutrients throughout the week, because your plants will not be growing as fast as a tank that is injecting CO2. Again, just make sure you are keeping up on those 50% water changes as we don’t want fertilizers building up in the aquarium.


Related Produts

Fertilizer and Aquasoils


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