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alright, so i have several questions. forgive me if any of this has been covered previously. i searched around the forum and have a general idea, but i wanted to ask a few specific questions. disclaimer: i understand that this hobby is very much trial and error until balance is achieved, so these questions are in assumption that light intensity, co2, and plant mass are perfect.

in regard to e.i. dosing:
i understand that the weekly 50% water change is to reset tank parameters. reset them to what, though? is the w.c. to reset all nutrients back to zero ppm or should one test the water immediately following a w.c. and use those readings as "zero" (or in other words the starting point to which one can say, "i will need ___ much n,p,k, etc. to achieve ___ ppm of each by the end of the week.")? i feel as though i've read a lot of mixed advice in that some people shoot for a particular ppm, and others say something similar to "add until you have an issue then back off."

in regard to macro-micro nutrient mixes:
i understand that this is basically all things needed, pre-mixed, less po4 as it's affected by the iron in the trace mix. is it safe to say that this mix is similar to a liquid n, p, & k mix (less traces obv.) i.e. one cannot alter the n, p, & k individually, that is added to the tank? i'm under the impression that if one were to use a macro-micro mix, they should add the po4 the following day as to not affect the nutrients. am i correct in assuming that one would follow a regimen of mix, po4, mix, po4, mix, po4, w.c.?

hopefully these questions make sense. :iamwithst
 

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All right, lets assume the numbers work perfectly. Here is the most basic scenario.

Add x amount of something to the tank every other day.
At the end of the week there is 3x of whatever you have added, minus what the plants have used. (Lets start with the assumption that the plants are not using anything, and there is no other way to remove whatever x represents)
Then you do a 50% water change. You have removed 1.5x, and remaining in the tank is 1.5x.

The following week, add x amount of something to the tank every other day.
At the end of the week there is 3x + the original 1.5x, for a total of 4.5x of whatever you have added, minus what the plants have used. (We are still working with the assumption that the plants are not using anything)
Then you do a 50% water change. You have removed 2.25x, and remaining in the tank is 2.25x.

You can go on this way, if you want. The end result is that the tank will START each week with 3x, build up to 6x, then on water change day you will return the tank to 3x.

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This boils down to:
A fertilizer will range from a low right after a water change to a high right before a water change.
The high is twice the low.

So, if you figure out the correct range for a certain fertilizer, you can figure out how much to dose every week, or divide by 3 to dose 3 days per week.

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Example:
Lets say you want to keep the NO3 between 10ppm-20ppm.
Then every other day you would dose 3.33ppm.

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Now lets add plants. (makes the tank SO much nicer!)

To figure out how much the plants are using through the week you would figure out how much you are adding, and what the ppm would be if nothing removed it.
Then test the water, and see how much is really there.
The difference is what the plants are using.

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Real life example, with a story.

I used to have tanks without plants. I was doing 50% water changes every week to get rid of the NO3. (I put it in the garden, so it was not being dumped down the drain- plants grew great outside)
Then I added plants. They were not happy.
Then I improved the conditions, including light, DIY CO2, but still had a LOT of fish in the tanks.
I added potassium and iron, but was still doing water changes to keep the NO3 down.
So I reduced the fish population in each tank (by getting more tanks and sharing the fish among them all)
Now the NO3 was hovering around 5-10ppm, and hitting 0ppm in some tanks.
I started doing EI.
The NO3 skyrocketed.
Since I already had a fair amount of NO3 in some tanks, I did not have to add more, so I adjusted the recipe.
Since some tanks were a lot closer to 0ppm NO3, I slowly added NO3 to these tanks until they also were hovering between 5-10ppm.

What I ended up with is something a lot closer to PPS-pro dosing. Much smaller amounts, and much smaller water changes.

Today, I allow a maximum of 20ppm before needing a water change.

The moral of the story:
Each tank is different, and you need to stay on top of the testing to really be sure of what is going on in there. Even tanks that are apparently set up the same, and run the same, do not always act the same.

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Buy each fertilizer separately. Then see what is needed.
If you are seeing a lot of NO3 from fish food, then reduce the ratio of N, P and traces, since fish food has a fair amount of these.
But dose P and Fe, since fish food is low in these.
Make sure the Ca and Mg are present in the right ratio for fish and plants. Plants use Ca and Mg in a 4:1 ratio. Do not blindly add Epsom salt (magnesium sulfate) without confirming that your tank needs it.
 

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Most people do macros together, and micros/Fe together, on alternate days. But you are right in thinking P is what you want to isolate from micros/Fe.

If you are seeing a lot of NO3 from fish food, then reduce the ratio of N, P and traces, since fish food has a fair amount of these.

But dose P and Fe, since fish food is low in these.

Make sure the Ca and Mg are present in the right ratio for fish and plants. Plants use Ca and Mg in a 4:1 ratio. Do not blindly add Epsom salt (magnesium sulfate) without confirming that your tank needs it.
I believe you meant to say K and Fe. :)

Nice informative post btw!
 

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It is not complicated.
Make notes of how much fertilizer in ppm was dosed before a water change. Then, how much water in % was changed after.

Now we have two numbers, dosed ppm and water change in %.

Example;
Mo 3 ppm dose
Tu 3 ppm
We 3 ppm
Th 3 ppm
Fr 3 ppm
Sa 3 ppm
Su 3 ppm
Sum before water change 21 ppm

ppm max = ppm dosed x (100 / % water change)

For 25% water change
ppm max = 21 x (100 / 25)
ppm max = 84

For 50% water change
ppm max = 21 x (100 / 50)
ppm max = 42

The final result [ppm max] is the highest ppm that can be reached in the aquarium water column.
 
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