[John N.]

Overview
The Estimative Index (EI) coined by Tom Barr is a straightforward method for providing nutrients for a planted tank. The idea behind EI is simply introducing an excess amount of nutrients within an aquarium, throughout the week. This excess of nutrients floods the water column and feeds the plants. This is an estimative method; measuring specific nutrient uptake rates is not necessary and no test kits are involved. EI provides a surplus of nutrients that helps to prevents plant deficiencies, and allows plant growth to out compete algae growth.

The process of which this is done is simple. Each day fertilizers are dosed, and the nutrients are absorbed by the plants. With this method being estimative, we can dose fertilizers according to general guidelines suited for our particular setup (see below). At the end of the week, one performs a 50% water change to 'reset' the nutrient load in the entire system. And then the entire dosing schedule is repeated.

The primary fertilizers are the macro nutrients - Nitrogen (N), Phosphorous (P), Potassium (K), and the micro nutrients - trace elements (Plantex CSM+B, Flourish). Iron (Fe) can also be supplemented if necessary.

The Estimative Index method works best for a high light and well planted aquarium. However it is not limited to lower light setups, smaller quantities of fertilizers should be dosed in those instances.

General Dosing Guideline for High Light and Well Planted Aquariums
(wolfenxxx)

10- 20 Gallon Aquariums
+/- 1/8 tsp KN03 (N) 3x a week
+/- 1/32 tsp KH2P04 (P) 3x a week
+/- 1/32 tsp (2ml) Trace Elements 3x a week
50% weekly water change

20-40 Gallon Aquariums
+/- ¼ tsp KN03 3x a week
+/- 1/16 tsp KH2P04 3x a week
+/- 1/16 tsp (5ml) Trace Elements 3x a week
50% weekly water change

40-60 Gallon Aquariums
+/- 1/2 tsp KN03 3x a week
+/- 1/8 tsp KH2P04 3x a week
+/- 1/8 (10ml) Trace Elements 3x a week
50% weekly water change

60 - 80 Gallon Aquariums
+/- 3/4 tsp KN03 3x a week
+/- ¼ tsp KH2P04 3x a week
+/- ¼ tsp (20ml) Trace Elements 3x a week
50% weekly water change

100 - 125 Gallon Aquarium
+/- 1 1/2 tsp KN03 3x a week
+/- ½ tsp KH2P04 3x a week
+/- ½ tsp (30ml) Trace Elements 3x a week
50% weekly water change

Note: K2SO4 is not required for dosing unless you need the extra Potassium (K). This K is found in KN03 and KH2P04. Dosing these two according to above will yield sufficient K levels. Therefore, one will be fine dosing only KN03 and KH2P04, and Plantex. If one needs to increase their K levels with K2S04, add the same measured amount as KH2P04. For example, if one is dosing 1/2 tsp of KH2P04, then dose 1/2 tsp of K2S04. In true regards to EI, added excess K is not detrimental in any event.

EI target ranges
CO2 range 25-30 ppm
NO3 range 5-30 ppm
K+ range 10-30 ppm
PO4 range 1.0-2.0 ppm
Fe 0.2-0.5ppm or higher
GH range 3-5 degrees ~ 50ppm or higher
KH range 3-5

Where to buy fertilizers?
AquariumFertilizers. com could have provide you with the necessary chemicals for dry and liquid dosing of the above but is out of buisness. For micro - trace elements, Plantex CSM+B, Seachem Flourish, and Tropica AquaCare are equivalent to each other. Drsfostersmith and bigalsonline for the Seachem and Tropica brands.

One Pound of each of Aquarium Fertilizer/Greg Watson's Chemicals will last at least 1 year:

Plantex CSM+B​

Potassium Nitrate KN03​

Monopotassium Phosphate KH2P04​

Potassium Sulphate K2S04 (optional)​

Special Notes:

Providing optimal CO2 levels of at least 30 ppm are necessary for plants to prosper and out-compete algae. If algae issue arise, remove all visible algae and infected leaves. Recheck CO2 levels, and possibly reduce and adjust the lighting period.

Direct dry dosing into the tank is perfectly fine. Many dosing straight into the tank, or they dissolve each chemical in water before adding.

Making a Liquid Stock of Plantex CSM+B is more often mixed into a bulk liquid solution since some find it more convenient to dose their trace elements this way. The recipe for this solution is 1 tablespoon to 250ml water is equivalent to: 20 ml = 1/4 teaspoon of dry Plantex. This solution is stored in refrigerators to prevent mold from forming within the container.

Small dosing teaspoons (smidgen, dash, pinch) can be found at Linen & Things, Bed Bath and Beyond, Wal-Mart, dollar stores, eBay and other online retailers. To identify the specific measurements of your smidgen, dash, pinch set, a 1/8 tsp should fill a ¼ tsp in 2 tries, 1/16 tsp in 4 tries, and a 1/32 tsp in 8 tries.

Stick to a good dosing regime and your plants will flourish!

 

[John N.]

That's correct, the measurements are made for dry dosing in teaspoons as described in the article. For liquid dosing of NPK, see the link provided above in the special notes section regarding liquid solutions. There is no difference either way in dosing methods; it's what is most comfortable and convenient for the user.

-John N.

 

[John N.]

Precipitate: KH2PO4 and Iron

Mike is correct,

• Adding KNO3 and KH2PO4 together will not cause problems. The above statement is mistaken when dosing in large bodies of water such as an aquarium. In small containers you might have an issue.

• Adding KH2PO4 and Fe (from traces) can cause a precipitate (white powder) to come out of solution. This chelated iron precipitate is now no longer available to the water column, and must now be taken up from the roots where the powder will settle.

• Mixing macro elements and trace elements in the same bottle forms a highly concentrated and volatile solution of chemicals in a small amount of water (500ml). This could result in precipitation, cloudy and ineffective mixtures. That's why we shouldn't mix the chemicals together in a small container.

Bottom line with dosing together: When dosing the chemicals (macro and micro) in our aquariums together, you won't have a problem because they are now in a very diluted solution. However to prevent any precipitation (cloudiness), we can dose macro and micros on off days so that each are consumed before the introduction of the other.

-John N.

 

[John N.]

The goal is to have at least 5 ppms of Nitrate per dosage. So by increasing the KNO3 mixed in the 250 ml solution, we can get 1 ppm per 1 ml dosed.

KNO3
12 g for 250 ml. 5 ml of stock solution dosed is 5 ppm of N, thereby hitting the target goal.

KH2PO4
Calculations above look good. However, instead of using the full 5ml dosage, only 2-3 ml 3x a week is needed.

-John N.

 

[John N.]

As you noted, the ppms per week represent the chemical accumulation without any plant uptake or consumption. Of course zero uptake is not what happens in our aquariums. The wide ranges listed above describe the daily totals with uptake that can happen through the course of a weekly dosage. What does that mean?

Plants consume a good amount of the nutrients in high light situations each day, however they can't eat all of it! From day one, the nutrient load climbs into the upper excess tiers by the end of the week. The 50% weekly water change flushes the system so that the levels are then reduced.

The more debated day to day range can be denoted as:

CO2 range 25-30 ppm
NO3 range 5-15 ppm
K+ range 10-15 ppm
PO4 range 1.0-2.0 ppm

-John N.

 

[John N.]

PO4 is dosed in low quantities and also consumed in low quantities, whereas the other chemicals have a wider range and wider range of consumption values. It can be stated that 3ppm of PO4 dosed between day 1 and the next dose on day 3 will be consumed to its depletion. I'm not sure if that makes sense to you, but I'm sure there will be a better explanation than mine coming along.

-John N.

 

[John N.]

For both Seachem Flourish and Iron, dose according to the directions on the bottle. Dose both on the micro element dosing days, and do the 50% waterchange at the end of the week as normal.

-John N.