Why Water Change with EI? - The Planted Tank Forum
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post #1 of 35 (permalink) Old 06-20-2011, 11:17 PM Thread Starter
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Why Water Change with EI?

What's the point of doing a water change with EI? Sure it's to "reset the tank" but what does this really mean? All I see is "halve the nutrients" and start "anew" when in reality you're technically just compounding the nutrients albeit slowly. I mean doing EI this way works, I've been doing it for almost a year now but I'm curious. What's the point of the water change? Why not just not fertilize for like 3 days or so?
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post #2 of 35 (permalink) Old 06-21-2011, 12:01 AM
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You are essentially resetting the tank to a low level of nutrients in the water. Remember the plants take in a good deal of fert's during the week, so you are not just halving what is in the water.


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post #3 of 35 (permalink) Old 06-21-2011, 12:09 AM Thread Starter
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Wait...you are mathematically halving what's in the water by doing a 50% water change at the end of the week. And if there's even an excess by the end of the week, why do a water change? Why not let the plants do the excess removal for you? The one reason I'd imagine is that one or two nutrients may have been depleted more than others and it would be important to do a water change then. But I don't understand this regimen:

sun - dose
mon - dose
tues- dose
.
.
.
fri- dose
sat- wc/ no dose
sun- dose

and so forth. Why? I mean doing a water change and letting the plants run down the nutrients are essentially the same thing? And who says you aren't just steadily building up nutrients? Who says that plants use XX% or so of the nutrients you put in per day? It's too variable. I know that EI is open for tweaking so why do we have water changes when not doing them would yield the same result albeit at technically 50% the rate?
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post #4 of 35 (permalink) Old 06-21-2011, 12:24 AM
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Call me stupid,

But what is "EI"

Bing search:

This is short for the Estimated Index and was invented by Tom Barr.
It is a simple method of adding regular amounts of fertiliser to planted aquariums virtually every day followed by a large water change weekly so that the aquarist knows that the plants have sufficient nutrients to grow healthily and so prevent unwanted algae growth.
To quote the site:
The Estimative Index (EI) 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 unhindered. Most algae related issues are due to plant deficiencies rather than excess nutrient levels(Ammonium/NH4 + is the exception).
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post #5 of 35 (permalink) Old 06-21-2011, 12:31 AM
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Quote:
Originally Posted by Jeffww View Post
Wait...you are mathematically halving what's in the water by doing a 50% water change at the end of the week. And if there's even an excess by the end of the week, why do a water change? Why not let the plants do the excess removal for you? The one reason I'd imagine is that one or two nutrients may have been depleted more than others and it would be important to do a water change then. But I don't understand this regimen:

sun - dose
mon - dose
tues- dose
.
.
.
fri- dose
sat- wc/ no dose
sun- dose

and so forth. Why? I mean doing a water change and letting the plants run down the nutrients are essentially the same thing? And who says you aren't just steadily building up nutrients? Who says that plants use XX% or so of the nutrients you put in per day? It's too variable. I know that EI is open for tweaking so why do we have water changes when not doing them would yield the same result albeit at technically 50% the rate?
as I understand it, you are not halving the total of the introduced fert. You are right, halving what is in the water at water change point. Given you rest day (7th day, just before water change) you are in essence giving the plants the chance to suck up all the left over nutrients within the water, thus leaving very little in the water at water change time to halve even more. I am not sure what I just typed makes sense lol.


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post #6 of 35 (permalink) Old 06-21-2011, 12:34 AM
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The whole point of this system is to not let your plants ever run "dry" of any particular nutrient. You could try and determine the exact uptake levels of your systems and then determine the exact dosing that is required to meet that, but there is multiple problems with that like regularly inaccurate testing results, measurement errors, changes in tank uptake, etc.

When you dose EI you always have enough nutrients to satisfy your tanks requirements, but never so much that you reach toxic levels. Obviously you don't want 200 ppm nitrates in your system and reducing everything by 50 percent each week prevents this from ever happening. Read Tom's article about it on his website the Barr Report. Yes you are "wasting" nutrients each week, but they are dirt cheap compared to testing equipment, and personally, my time.
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post #7 of 35 (permalink) Old 06-21-2011, 12:36 AM
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I have seen this question on a few occations... Totally normal question and understandable. The beauty with dosing EI is,.... Who cares? No need to test. Do larger water changes if you would like. I actually do 80% water changes at least once a month. I was doing them weekly but realized that it was just a waste of water. I just like to keep my tanks clean. OCD maybe...

If you have a heavily planted tank, with good lights and good co2, your plants will take in lots of the ferts. Even with some build up, you will be fine. I wouldn't suggest dosing EI and 50% water changes on a tank with 2 plants and a single T8 bulb. You are trying to keep all nutrients at a non limiting level without having to constantly test the water. If you don't mind spending money on testing the water daily with calibrated test kits(if you don't calibrate them yourself, they are worthless), then go for it. That just seems to be more work then is actually needed and will get old very fast, IMO...

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post #8 of 35 (permalink) Old 06-21-2011, 12:39 AM
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Originally Posted by Higher Thinking View Post
The whole point of this system is to not let your plants ever run "dry" of any particular nutrient. You could try and determine the exact uptake levels of your systems and then determine the exact dosing that is required to meet that, but there is multiple problems with that like regularly inaccurate testing results, measurement errors, changes in tank uptake, etc.

When you dose EI you always have enough nutrients to satisfy your tanks requirements, but never so much that you reach toxic levels. Obviously you don't want 200 ppm nitrates in your system and reducing everything by 50 percent each week prevents this from ever happening. Read Tom's article about it on his website the Barr Report. Yes you are "wasting" nutrients each week, but they are dirt cheap compared to testing equipment, and personally, my time.
lol that's in essence what I was trying to say... but much more confusing even to myself. (I hate monday's with a high work load, makes me brain dead by evening)


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post #9 of 35 (permalink) Old 06-21-2011, 12:46 AM Thread Starter
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I have what you call a "heavily planted" tank (you can't see the back of the tank) and I rarely bottom out and most the time I'm reading 60-70ppm nitrates no matter the day of the week.
But here's my logic:

The intention is to let the plants take out excess nutrients and prepare them for the next week of dosing. This is done by halving the nutrients and letting the plants run them down sufficiently so that they'll be replenished to a non-toxic (pretty much impossible to do even without water changes) level. Thus the assumption is that the plants use 50% of the residual weekly nutrients in one day.

My counter assumption is that why not just not dose for two days and be done with water changes?
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post #10 of 35 (permalink) Old 06-21-2011, 12:51 AM
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Quote:
Originally Posted by Jeffww View Post
I have what you call a "heavily planted" tank (you can't see the back of the tank) and I rarely bottom out and most the time I'm reading 60-70ppm nitrates no matter the day of the week.
But here's my logic:

The intention is to let the plants take out excess nutrients and prepare them for the next week of dosing. This is done by halving the nutrients and letting the plants run them down sufficiently so that they'll be replenished to a non-toxic (pretty much impossible to do even without water changes) level. Thus the assumption is that the plants use 50% of the residual weekly nutrients in one day.

My counter assumption is that why not just not dose for two days and be done with water changes?
Go for it. Nothing wrong with that. You can watch your plants and see how they react. If that works for your tank, great. If you start noticing deficiencies, then you will just have to adjust.

How do you know that you 70ppm of nitrates? Unless you calibrated your test kit, those results are worthless.

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post #11 of 35 (permalink) Old 06-21-2011, 12:55 AM Thread Starter
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I've callibrated to my own tank. Quite simply I took my empty tank. Used RO/DI water filled it up and dosed on the first day a concentration I knew. That's been my baseline ever since. I've double checked by doing the 50% and noted the loss. I know it's inaccurate but only maybe 20-30% error. Not enough to matter for our uses.
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post #12 of 35 (permalink) Old 06-21-2011, 01:05 AM
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Originally Posted by Jeffww View Post
I've callibrated to my own tank. Quite simply I took my empty tank. Used RO/DI water filled it up and dosed on the first day a concentration I knew. That's been my baseline ever since. I've double checked by doing the 50% and noted the loss. I know it's inaccurate but only maybe 20-30% error. Not enough to matter for our uses.
I think I understand what you are saying but I am not sure that we are on the same page. I could be wrong though. So you dosed your tank with kno3 to reach a known ppm of nitrates? How big is the tank and how much did you dose to get that reading?

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post #13 of 35 (permalink) Old 06-21-2011, 01:07 AM
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Quote:
Originally Posted by Jeffww View Post
I have what you call a "heavily planted" tank (you can't see the back of the tank) and I rarely bottom out and most the time I'm reading 60-70ppm nitrates no matter the day of the week.
But here's my logic:

The intention is to let the plants take out excess nutrients and prepare them for the next week of dosing. This is done by halving the nutrients and letting the plants run them down sufficiently so that they'll be replenished to a non-toxic (pretty much impossible to do even without water changes) level. Thus the assumption is that the plants use 50% of the residual weekly nutrients in one day.

My counter assumption is that why not just not dose for two days and be done with water changes?
The intention is never to let your plants take out excess nutrients. That is the point, that there is always going to be an excess, never deficiencies. The assumption is not at all the plants will use 50% of the nutrients. That is the awesome part about EI. Even if you use none of them you cannot reach toxic levels, for example:

Say you dose 20ppm per week, 0% percent uptake will leave you with 20 which you will half=10ppm
Dose all week til you have 30ppm; 0% percent uptake will leave you with 30 which you will half=15ppm
Next week end with 35, half to 17.5
Following week end with 37.5, half to 18.75
18.75-->38.75, half to 19.375.

Eventually these numbers level out to where any increase in negligible.
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post #14 of 35 (permalink) Old 06-21-2011, 01:15 AM Thread Starter
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I think I understand what you are saying but I am not sure that we are on the same page. I could be wrong though. So you dosed your tank with kno3 to reach a known ppm of nitrates? How big is the tank and how much did you dose to get that reading?
Standard 60p so like 17.6 gallons. I arbirarily dosed 1g of kno3 into the tank. And then used some mass conversions to get my predicted ppm. Did my test. Saw it was generally in the range and assumed it was okay. Did my water change saw that it dropped to the 5-10 mark and decided it was okay. This was all done during my leak test so there were no factors like plants and fish or anything.

And at the above person. If the intention is to never let any nutrients crash why don't we dose on water change day? What's the difference between just not dosing for two days and not dosing and doing a 50% change on one day.
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post #15 of 35 (permalink) Old 06-21-2011, 01:20 AM
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My schedule is:
W/C, then Macro
Micro
Macro
Micro
Macro
Micro
Off Day
The only reason you don't dose on a everyday is because you know that your system is satisfied with fulfilling the EI estimates for that tank size. I don't think anyone ever said to not dose on WC day. In fact I think that is a must. Like I said, read the report on the Barr Report. Straight from the mouth of the mind behind it all.
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