Dosing dry ferts

Blinky

Blinky

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I've been trying to wrap my head around fertilization (given up trying to create liquid stock solutions, just can't get it to work) and I think between several online calculators I've got a handle on amounts of dry compounds to dose.
My question now is what's the best way to add the ferts - I don't want to burn my plants/fish, so I'm wondering, is it best (or necessary) to mix dry compounds with water, rather than just them adding straight to the tank?
My plan is to dose macros and traces on separate days to avoid the problem of PO4 and Fe binding to create insoluble FePO4.
While I'm at it, if anyone can help me with the amount of CaNO3 to add, I'd be really grateful - I can't find info for this anywhere. My tap water has 20ppm Ca, the GH is ~100 so as I understand it, the ratio of Mg and Ca is quite off. My plants have been showing signs of Ca deficiency, so I'd like to get the Ca to 30ppm or more. I was going to start with 1tsp in my 65g and go from there - any thoughts?
 
I'm pretty sure you'd want to dissolve the dry ferts into a small amount of water before dosing it into your tank.

I'm not sure on how likely the FePO4 would form, but I guess it's always good to avoid it if there's a possibility that it'll form.

I'm not exactly sure on the amount of Ca(NO3)2 you want to be adding right now (as I just woke up, and am too lazy to try and calculate it right now). However, I'd be wary of using it to supplement your Ca levels due to the fact that it packs quite a punch in terms of NO3 supplementation. Are you adding KNO3 or anything else that has NO3? If so, you might not want to use the Ca(NO3)2. Instead, you could try using CaCl2 for the calcium supplements.

Alternatively, I have heard of people using cuttlebones as calcium supplements (but I believe it does harden the water slightly).
 
Thanks for the heads up, I'm going to try to find another source of Ca to use together with the CaNO3 - I think I need quite a bit to boost the small amounts in our tap water, and don't want the NO3 to get too high. The tank is high light, packed with plants and NO3 disappears pretty quickly, so I don't mind having it slightly over 10ppm until I can get to the hydroponics shop :)
I mixed up the KNO3, KCl, KH2PO4 and MgSO4 (just a bit, for the S more than the Mg) in 500ml of water, and poured it into the tank.
A degree in chemistry sure would come in handy right about now ;)
 
Blinky,
To calculate how much to add first select a target NO3 conc, I'll call this T in the equation below, it has units of mg/L (ppm)

Next, you need to know your tank volume in L, I'll call this V.

Finally, you need to know the mass fraction of Ca(NO3)2 as NO3, I'll call this % (Ca(NO3)2=0.7558 NO3)

g Ca(NO3)2 =T*V*0.001/%

So for your 65g tank:
g Ca(NO3)2 = [10mg/L*246L*0.001g/mg]/0.7558
Add 3.25g of Ca(NO3)2 to get 10ppm NO3 in your 65g tank. Dissolve it in some water first.

This will add about 3ppm of Ca to your tank.
ppm (Ca) = ppm NO3*%(Ca)/%(NO3)

Basically it's just the mass percent ratio of the two nutrients.
 
Wow, thanks! That may take me a while to grasp fully, but it's very helpful. I really do feel like I'm in need of some chem classes, I never realized how in-depth this hobby can get!
 
Not bad, but this is my U2 favourite of all time:

You say
Love is a temple
Love a higher law
Love is a temple
Love the higher law
You ask me to enter
But then you make me crawl
And I can't be holding on
To what you got
When all you got is hurt
 
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