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Discussion Starter #1
Hello everyone,
I have recently started dosing my aquarium according to PPS PRO mix on daily schedule.

The recipe on GLA website per 500mll bottle is as follows:
K2SO4 – 29.3 grams
KNO3 – 32.6 grams
KH2PO4 – 2.9 grams
MgSO4 – 20.2 gram

One thing that seemed weird to me from beginning was the 2.9 gramms of PO4, which seems kind of low. Also, according to GLA, a daily dose of 1ml per 10 gallons should keep the level of PO4 around 1.4ppm.

I went to Rotala Butterfly and calculated following, 2.9 gramms of KH2PO4 to a 500mll then chose dose size of 7.5mll (meaning 1mll per gallon for my 75 Gallon tank) and the dose result was 0.11ppm per dose (screenshot attached). Now 0.11ppm mutiplied by 7 days = 0.77ppm total dose per week and this doesn't account for PO4 consumption during this time.

So I don't understand how is the PPS PRO recipe supposed to maintain the PO4 levels at 1.4ppm???

Am I not understanding something or the recipe is not correct?
 

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Mark Fisher, scroll down, it is down there.

Also, according to GLA, a daily dose of 1ml per 10 gallons should keep the level of PO4 around 1.4ppm.

So I don't understand how is the PPS-Pro recipe supposed to maintain the PO4 levels at 1.4ppm???
It is not “around” nor “at”. It is upper limit, the maximum concentration. GLA is correct, they took the information from here How to do PPS-Pro with water changes?

Look at it this way, what are we adding to the aquarium every week? We are adding 50% water and 0.1 ppm x 7 days = 0.7 ppm per 100% water. So in reality, we are adding weekly 0.7 ppm x 2 = 1.4 ppm and this is why it is the upper limit. Makes sense?
 

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Discussion Starter #5
Edward,
Why did you multiply 0.7ppm by 2? I don't understand where that comes from.

@Edward,

Look at it this way, what are we adding to the aquarium every week? We are adding 50% water and 0.1 ppm x 7 days = 0.7 ppm per 100% water. So in reality, we are adding weekly 0.7 ppm x 2 = 1.4 ppm and this is why it is the upper limit. Makes sense?
 

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What are we adding every week? We are adding 50% water volume and also adding 0.7 ppm / 100% water volume. So if we were going to premix this water before adding it into the aquarium, what ppm it would be? It would be 100 / 50 x 0.7 = 1.4 ppm. We are supplying the aquarium with water that has 1.4 ppm and therefore the ppm cannot get any higher from the fertilizer than 1.4 ppm.

If we were changing 25% water weekly then 100 / 25 x 0.7 = 2.8 ppm.
If we were changing 33% water weekly then 100 / __ x 0.7 = __ ppm. You fill the blanks.

Good?
 

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Discussion Starter #7
I am more confused. When doing water changes I am supposed to premix the new water with fertilizer before adding to the tank? I don't remember seeing this in the guide.
The guide says:

"Dose PPS-Pro Solution #1 and PPS-Pro Solution #2 at the same time daily for a week, then 50% water change."

So, I dose 1ml per 10 gallon for a week. This gives me a value of 0.7ppm at the end of the week. Then I do 50% water changes. This means 0.7 / 2 = 0.35ppm (because the new water doesn't contain any fertilizer) + a new dose of 1ml per 10 gallon that day means 0.35+0.11 equal 0.46ppm.

What are we adding every week? We are adding 50% water volume and also adding 0.7 ppm / 100% water volume. So if we were going to premix this water before adding it into the aquarium, what ppm it would be? It would be 100 / 50 x 0.7 = 1.4 ppm. We are supplying the aquarium with water that has 1.4 ppm and therefore the ppm cannot get any higher from the fertilizer than 1.4 ppm.

If we were changing 25% water weekly then 100 / 25 x 0.7 = 2.8 ppm.
If we were changing 33% water weekly then 100 / __ x 0.7 = __ ppm. You fill the blanks.

Good?
 

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I am more confused. When doing water changes I am supposed to premix the new water with fertilizer before adding to the tank? I don't remember seeing this in the guide.
The guide says:

"Dose PPS-Pro Solution #1 and PPS-Pro Solution #2 at the same time daily for a week, then 50% water change."

So, I dose 1ml per 10 gallon for a week. This gives me a value of 0.7ppm at the end of the week. Then I do 50% water changes. This means 0.7 / 2 = 0.35ppm (because the new water doesn't contain any fertilizer) + a new dose of 1ml per 10 gallon that day means 0.35+0.11 equal 0.46ppm.
people math differently; people view things from different angles. I guess it's what makes life interesting.

Let's look from your angle:

you said:
This means 0.7 / 2 = 0.35ppm (because the new water doesn't contain any fertilizer) +
a new dose of 1ml per 10 gallon that day means 0.35+0.11 equal 0.46ppm.

but you need to keep going.
day 2 0.46 + 0.11 = 0.57
day 3 0.57 + 0.11 = 0.68
day 4 0.68 + 0.11 = 0.79
day 5 0.79 + 0.11 = 0.90
day 6 0.90 + 0.11 = 1.01
+ rounding up (0.04) -- because you guys did it and it keeps the example more consistent...
day 7 water change 1.05 / 2 = 0.525
repeat above for a week
0.525 + 0.7 = 1.225
water change and repeat
1.225/2 + 0.7 = 1.3125
1.3125/2 + 0.7 = 1.36
1.36/2 + 0.7 = 1.38
1.38/2 + 0.7 = 1.39
1.31/2 + 0.7 = 1.395
1.395/2 + 0.7 = 1.3975
..
..
..
..
..
really close to 1.4! but as @Edward mentioned, it'll never exceed it.

It's one of those wonderful tricks of math. Where, if you add something and divide by 2, and add it again, and keep repeating, you'll get closer and closer to doubling it.

Perhaps it's more fun to graph it on the same rotalabutterfly site

https://rotalabutterfly.com/accumulation-calculator.php

plug in the numbers



of course, if you talk about consumption, then .. that's another can of worms.
 

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And because we don’t know how much fertilizer will be taken up by plants, it is a good idea to monitor TDS. Fertilizer additions increase TDS, plant uptake and water changes decrease TDS. Good balancing is when dosing little more than needed while changing as much water as necessary to prevent TDS rising. Some setups need less water changes and some may need more.
 

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Discussion Starter #11
I understand the theory behind measuring the TDS but there are many factors that can affect TDS so I don't feel it accurate enough to rely on.

For instance water evaporation, how do we know how much water evaporates during a day? In order to have an accurate TDS reading the evaporated water needs to be refilled using distilled water in the same amount that has evaporated. Besides, the substrate can leech and in my case the tank is dirted. Who knows what's sipping out of it...

Indeed my TDS is going up about 30ppm during the week and is consistently about 70ppm higher than my tap water.

And because we don’t know how much fertilizer will be taken up by plants, it is a good idea to monitor TDS. Fertilizer additions increase TDS, plant uptake and water changes decrease TDS. Good balancing is when dosing little more than needed while changing as much water as necessary to prevent TDS rising. Some setups need less water changes and some may need more.
 

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Discussion Starter #13 (Edited)
They are a good reason, and that's why I am doing it regularly. What I am saying is that TDS reading is not accurate enough to measure plants uptake or fertilizer accumulation.

vanostav61
You think TDS increase due to water evaporation and substrate leaching are not good reasons for water changes to return TDS to previous level?
 
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