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Estimative Index Dosing Guide

469883 Views 224 Replies 99 Participants Last post by  mistergreen
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

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!
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Assuming you have average tap water, you need KNO3 and KH2PO4. You also need a source of trace elements, which can be Greg Watson's CSM+B or it can be a commercial trace mix, such as Flourish. Your big tank will go through commercial trace mixes pretty fast, so CSM+B would be the best idea. Assuming you have about 300 watts of PC quality light with good reflectors, I would start by dosing 2 tsp KNO3 3X per week, 3/4 tsp KH2PO4 3X per week, and 1/2 - 3/4 tsp CSM+B (dosed dry) 3X per week. If you have much lower light than 300 watts, I would cut down to 2X or less per week. If your water has a low GH, or little or no Mg component of the GH I would dose Greg Watsons Barr GH builder too.
I have a 5 gal tank. Now How much will i have to dose as far as the table spoon goes? how do i convert tsp to Gram, i have a neat little scale that can measure gram by 0.01, so i like to just use my scale. Thanks in advance!
One of the premises behind EI is that the exact amount of fertilizers dosed isn't at all critical. Everything is estimated. The easiest way to do a small tank like a 5 gallon is to get a bottle, say a 500 ml bottle, with a 5 to 20 ml cap. Measure how much the cap holds. Then divide 500 ml by what a cap holds, and that is the number of doses per bottle. Now multiply that number of doses by the amount of each dose of each macro fertilizer, and add that much to the bottle. Fill with water and shake it up good. Then dose a capful every other day or 3 times a week. Do the same for the micros. If you want to play with the gram scale, measure out a teaspoon and weigh it. That tells you how many grams each 1/8th, 1/4 etc. tsp is.

A variation of this, and what I use, is to take the total weeks dosage (3 times what each of the above doses is). Divide that by 7 and multiply by the number of capfuls in a bottle. That will be the amount to add when you want to dose the same every day, 7 days a week. You can dose the macros and micros on the same day also - the doses are weaker and the precipitation problem with iron and phosphate becomes trivial. But, don't mix micros and macros in one bottle - the concentrations there are great enough to precipitate all of the iron out as sludge in the bottle.
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I have always found that my fish enjoy the water changes, being more vigorous and active after such a change than before. I use Seachem Prime to get rid of chlorine or chloramine if I do a big change. I don't know if all such conditioners are equally good. Oh, and I don't make a big effort to match temperatures either. During the cold months I mix hot and cold to get somewhat near the tank temperature, but in the hot months I just use cold water most of the time. It may be that some species of fish are more sensitive to water changes than mine.

I have used CSM+B for two years + now, without any problems that I can see. Were you dosing it dry or mixing with water? I use dry most of the time, but am now premixing so I can dose an easy to measure amount of liquid every day. Flourish may be a better trace mix, but not by a whole lot.

I now use a continuous water change system, so I only do big changes when I do major maintenance on the tank. That works extremely well for me.
See less See more is the water change system I use now.

If you add the water conditioner to the half full tank before adding any new refill water it will protect the fish from chlorine/chloramine better.

The only test kits I have are GH, KH, pH.
Apologies if this has been covered and I just missed it, but is there any real reason not to use half the recommended amounts 6 days a week rather than the recommended amounts 3 days a week-- so long as you don't let strong concentrations of phosphate and iron mix.

It seems to me that that would be a simpler to keep track of.
There is no magic in dosing 3X a week, alternating between macros and micros, and letting the tank rest one day, then changing 50% of the water. You could have problems trying to dose a high light intensity tank only once a week - there is a good chance of running short of some nutrients that way. But, dosing daily, by dividing up the weeks total for each nutrient into sevenths, is a good way to do EI dosing. It also isn't necessarily bad to dose the iron containing micros the same day you dose the phosphate containing macros. The problem is when you mix those in a bottle so you can dose one pre-mix of all of the nutrients. Then the iron and phosphate will combine leaving an insoluble precipitate.

I have switched to the daily dosing method, using a premix of the macro nutrients, and one of the micro nutrients. I dose one at the right end of the tank and the other a few seconds later at the left end of the tank. My plants continue to grow.
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One of the best bottles to use for premixed fertilizers is the type Tropica Plant Nutrition Liquid comes in. You just squeeze the bottle to fill a small chamber at the top with the number of ml's you need, then pour the liquid in that chamber into the tank. Mine is marked at 10, 15, 20, 25 ml, and I dose 20 ml a day. So, the bottle contains 250 ml of fluid, and I dose 20 ml a day, so the bottle contains 12.5 doses in it. Multiply 12.5 doses times the amount of fertilizer per dose and add to the bottle, then fill the bottle with water. You can mix everything except the iron and traces in one bottle, and the iron and traces in another bottle.
I dosed 15 ml per day of premix for a few months, and had no problem with dissolving the chemicals for a 45 gallon tank. So, a 30 ml dose could obviously be set up with no problem for a 90 gallon tank. And, I suspect you could use an even smaller daily dose. The NPK part of the nutrients is inorganic so it will last forever without refrigeration. It is only the chelators that are organic, and they are only in the trace mix.
So if I convert every (tsp dosage to ml and multiply by three)/7 is that my dosage ml per day? :rolleyes:

I'm just trying to find out how you came up with the 20ml per day dosage.
Note: I will be using a 500ml bottle for each fert, trace.

1/4Tsp-KN03 3x a week
1/16+Tsp-KH2P04 3x a week
1/16+Tsp K2S04 3x a week
5ml Trace 3x a week
1-2ml Fe/Iron 3x a week

I think my only problem (once I figure out my solution portions) will be now is finding a pump that will give me a small amount of ml on each pump.
You are correct about figuring out the daily dose starting with the 3X per week dose. The amount of each dose depends on being sure it is big enough to dissolve all of the stuff you want in it, and something you can easily measure, either as a per squirt, or per capful, or per syringe full. There are pump bottles available, so you would just have to measure how much one pump gives, and use that as the per day quantity, unless that is too small to dissolve all of the ferts. In that case, use two pumps per dose.
It is the TMG, now known as Tropica Plant Nutrition Liquid. It could also be CSM+B, a cheap powdered trace mix.
EI was designed for high light, CO2 injected, heavily planted tanks. When you adapt it for lower light, no CO2, and lightly planted tanks, you can't use the tables in the sticky. As I recall, the usual plan is to dose only once a week, and dose somewhat less than the dose recommended for 3 times a week. That also means you don't need weekly 50% water changes, but monthly would be more like it. By then it isn't really EI.
Yes, EI should work for you. If your planting density is low, just cut the amounts in half. "Root feeders", like almost all plants, absorb nutrients from the water too. Root tabs or a nutrient rich substrate are good, and they make it less critical when you forget to dose for a couple of days, but you can grow those plants with just water column dosing too.
Hi, do you really need to dose Ca and Mg if you have a GH value of 5-6? Thanks
Since GH doesn't tell you whether you have zero magnesium or a lot of magnesium, it can be desirable to dose magnesium even with a GH of 5 degrees. I can find out how much I have, on average, in my tap water from my water quality report. The report also gives the range of values that might exist throughout the year. Since, my range can hit zero, I dose some epsom salts to be sure I have magnesium in the water.
Re: I probably don't know what I'm doing?

Something doesn't seem right with the EI dosing guides. For example:

For a 100 -125 gal tank
+/- 1 1/2 tsp KN03 3x a week
+/- ½ tsp KH2P04 3x a week
+/- ½ tsp (30ml) Trace Elements 3x a week

When I use the fertilator and the values: 1 1/2 tsp KN03, 1/2 tsp KH2P04 and a 110 gal tank, I come up with these ppm increases:
NO3 11.49
PO4 4.69
K 9.18

Isn't PO4 way too high?

Also 1/2 tsp is only 2.5 ml not 30 ml? Isn't 30 ml of trace way to high?
The numbers for trace elements are 1/2 tsp if dosed dry, or 30 ml of a mix of trace mix in water. I don't remember what the "standard" mix in water is, since I never do that.
Re: I probably don't know what I'm doing?

That make sense but the diluted formula calls for 3 tsp (1 tbl) dissolved in 250 ml.
That means adding 30 ml is too low:

3tsp/250ml x 30ml = 0.36 tsp.

I think you want to add 40 ml:
3tsp/250ml x 40ml = 0.48 tsp

I doubt this will make much of a difference.

Do you have any take on the PO4?
I didn't comment on the PO4 because I have been dosing about 1.5 to 2X the EI dosage on PO4 to help control GSA. From what I have been reading, there is nothing wrong with dosing 1/2 tsp for a 100 gallon tank. When you consider the range of tank sizes the dosages are given for, it is obvious that accuracy in dosing isn't important. Tom Barr always says these dosages are just starting points, and you can start reducing them a bit, watching for adverse results, reducing a bit more, etc. I don't do that because I haven't been good at keeping my plant mass nearly constant. The increased plant mass as the plants take off means you need more fertilizer anyway.
If you want to switch to the EI method you need to do so. Switching to that method means dosing more than the minimum of each nutrient, then doing about a 50% water change every week to avoid a too high build up of any of the nutrients. So, you should dose:
1 tsp of KNO3 three times a week
3/8 tsp of KH2PO4 three times a week, along with the KNO3
3/8 tsp of CSM+B three times a week on different days from the above dosing.

If you want to stick to 15-20% water changes every 3 weeks, you can't dose per EI. Then you need to look into PPS Pro as an alternative.
If my nitrates are already high (about 50) should I still add the KN03?
If your nitrates are already high you should calibrate your nitrate test kit, by verifying that it gives the right concentration when checked against solutions with known concentrations of nitrate in them. Only then can you know that your nitrates are high.

50 ppm of nitrate in a well planted tank will be used up in less than two weeks, so unless you have a known continuous source of nitrates, such as a heavy fish load, you will still need to add nitrates.
You should be dosing a lot bigger dosage of K2SO4 and/or KNO3 than KH2PO4. So, it is difficult to uniformly mix appropriate dry quantities of those chemicals so that each half teaspoon you scoop out contains about the right ratio of each. Mixing liquids is very easy, but mixing dry powders isn't. It isn't really that hard to dip out the tiny amounts of each of the powders individually on whatever schedule you follow. I keep mine in polyethylene containers, with snap on lids, with the content of the container and the dosage boldly marked on the lid.
It depends on how much of a drip you have going. If it is one gallon per day that is considerably different from 10 gallons per day, etc. The greater the rate you change the water the more likely you can dose according to the tables. At a gallon per day you would need to adjust the dosing to avoid big overdoses.
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