# EL dosing help



## wormvortex (2 Jul 2020)

Hi,

Looking to buy the EL starter kit from aquarium plant food and it's saying add:

1tsp Potassium Phosphate

to 500ml of water and dose 3x a week yet when I use the EL calculator on this site it is telling me to add 46 grams worth which is obviously way way more. Why is it so much more than the other site is suggestion and which is right. Or am I using the calulator wrong. It's for a 20Gallon tank.


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## hypnogogia (2 Jul 2020)

You’ve  entered potassium nitrate on the calculator, not potassium phosphate. Potassium phosphate is KH2PO4.  Potassium nitrate in KNO3. You’ve also selected to dose smaller amounts of liquid than the recipe from aquarium plant food uses, so it is more concentrated.


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## wormvortex (2 Jul 2020)

I didn't bother changing the amount of liquid because it wouldn't have explained the huge difference but picking the wrong chemical would! Thanks for noticing. Using KH2PO4 I get just over 1tsp worth.


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## wormvortex (5 Jul 2020)

One other question. My tap water already has high nitrates. Instead of adding KN03 as a macro could I instead add K2S04 as that would still allow me to have enough Potassium or am I missing something else that KN03 adds to the aquarium?


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## dw1305 (5 Jul 2020)

Hi all,





wormvortex said:


> My tap water already has high nitrates. Instead of adding KN03 as a macro could I instead add K2S04 as that would still allow me to have enough Potassium or am I missing something else that KN03 adds to the aquarium?


No, once they are in solution all potassium (K+) ions are the same, it doesn't matter what compound they came from. Usually you would add KNO3 just because both the cation (K+) and the anion (NO3-) are useful.

Your tap water will almost certainly supply some potassium as well (<"possibly as much as 5ppm">), but there isn't a regulatory limit for potassium so the water company doesn't report its level. 

It is easy to test for in the lab. via <"flame photometry, AAS or ICP">.

cheers Darrel


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## Zeus. (5 Jul 2020)

wormvortex said:


> One other question. My tap water already has high nitrates.



Yes many water supplies do, so on WC day if your tap water has 20ppm NO3 and you do a 50% WC you will have just dosed 10ppm NO3.

For this reason I dose Micros after WC then Macros the next day then Mic, Mac, Mic, Mac, Mic. Thereby leveling out the [NO3] throughout the week.  I am also a fan of dosing seven days a week as with an auto doser I dont need a rest day and IMO it helps maintain a better balance of the water parameters.



wormvortex said:


> K2S04 as that would still allow me to have enough Potassium



A good chioce  of 'K' IMO cheap as chips as well from ebay.

We do have a Fert calculator which takes the [NO3] from your water report when calculating the weekly ppm target, the present version does have a few minor bugs but may be worth a look ( New version is a little over due but we are working on it all the time)


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