Rotala butterfly K dosing confusion - The Planted Tank Forum
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post #1 of 3 (permalink) Old 10-06-2018, 01:02 PM Thread Starter
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Rotala butterfly K dosing confusion

Hello all.

I'm trying to figure out how much to dose with Ei in my 30 gallon, high tech and heavy planted tank.

I have the following salts from AquariumPlantfoodUK:
Chelated Trace mix

I actually have 2 questions that confuses me:

If i click on "Estimative index" in the "i am calculating for" when dosing MgSO4.7H2O, it says to dose 5ppm (5,68 gram), 2-4 times a week. I dose 3 times a week, so that would be 15ppm a week. But how i understand Ei ppm targets, it should be something like 5-10ppm Mg?

Obviously i could just type in "Dose to reach a target" of maybe 3ppm per dosing, and reach 9ppm Mg every week. It just confuses me the two are so far apart in ppm targets. I have always followed Rotala Butterflies' requested 5ppm per dose/15 ppm a week, but it looks like that would be too much?

Now that i look closer into how much ppm of what i put in my tank, i can see on Rotala butterfly, that dosing KH2PO4 1.3ppm 3x a week (3.9ppm weekly), and KNO3 7.5ppm 3x a week (22,5ppm weekly), will only give me 15.8ppm of K weekly. And the typical Ei is 20-30ppm?

Do i need to buy more K in the form of something like K2SO4?

Hope you guys can help, i've been struggling with this as i'm not very good with numbers.

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post #2 of 3 (permalink) Old 10-06-2018, 01:27 PM
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1. Where it says "dose these levels 2-4x week" or whatever, that is sort of a default instruction whenever you calculate something for EI. It doesnt necessarily apply to every nutrient in a literal sense. In the case of Mg, 5-10 ppm per week should be plenty for most tanks.

Also it depends on how much, if any, is in your tap water. That counts too. Obviously if you're using 100% RO you're starting with zero, but most tap waters have some Mg present. If your tap has 10-15 then you probably dont need any additional. if your tap has 4, like mine does, then an extra 5-7 per week would probably be good.

How much Mg you need also depends on how much Ca is present. Ratios are not super important but you'll need more Mg with 40 ppm Ca than you will with say 15

Generally speaking, if you dont know any of the above as it pertains to your tap water, adding an extra 5-10 ppm Mg per week should be a safe bet. 15 probably wont hurt anything but you really dont need that much in most cases.

2. Some people can get by with only the K in KNO3 and KH2PO4. Most find that adding additional K is better. A lot of EI users are also adding a commercial GH booster with Ca, Mg and K. Most of these boosters contain a lot of K, so if you're using something like that raising GH a couple of degrees you're probably getting plenty of total K

Otherwise, yes I would suggest adding some additional K2SO4 to get total for the week around 25-30 ppm
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post #3 of 3 (permalink) Old 10-11-2018, 03:15 PM Thread Starter
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Wow, i could've sworn i checked for answers during the day of my post and the day after.. I didn't see anything..

Anyway, thank you a lot! Really nice and helpfull reply. I have no idea what Mg and Ca is in my tap water, so i'll shoot for 9ppm Mg per week.

I'm not adding any GH booster, my tap is pretty hard. So now i've ordered some K2SO4, so we'll see if the plants will like it or not.

Thank you and good day
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