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It has been said low nitrates are a reason Java Fern turns brown and gets holes in the leaves. I went to Jons Plant Factory to get a product to help raise nitrates. I couldn't remember exactly what I needed and they didn't have any idea either. They knew a couple fish tank enthusiasts come by but didn't know what they were buying. Not wanting to go across town again, I bought some Calcium Nitrate (CaNO3), a 150 gram container for 6 bucks and change. Not real expensive in case it was the wrong product. Not knowing how much to put in my tank, I started reading and see maybe it was Potassium Nitrate (KNO3) I should have been getting.

Can I please get some insight into whether I should use the CaNO3 and how much to add to my 66 gallon tank. No CO2, just using Flourish and Metricide. I'll go and get some KNO3 if necessary.

I got the CaNO3 yesterday and have not put any in the tank. Sundays have been water change day, 20-25 gallons. The nitrates are always very low, 5ppm or so using an API liquid test kit. I've considered not changing water so often to let them build up a little, but I try to keep up with water changes since it ranks rather high on the list of aquarium rules.
 

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its not really which is better, it is which you prefer. They both dose nitrate, you just get to choose, do you want calcium or potassium with it ;)

however i'd recommend getting Potassium Sulphate (K2SO4) since you have the CaNO3 already. Normally they recommend KNO3 simply because when dosing phosphates and nitrates, you cover your potassium levels atleast. Many still dose more potassium than needed without any ill effects on the tank.

probably will be the same dosage, try this:
¼ teaspoon (1.4 grams) will add 22.5 ppm of nitrates and 14.26 ppm of potassium to 10 gallons of water. do the test, see if its the same, if it is then you are good.

Just dont think you can buffer your water with CaNO3, i believe it'll be 60 ppm of nitrate before you get 1 degree of hardness out of it, lol
 

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Depends on what CaNO3 you got. 13.0% or 15.5%

15.5 contains ammonium which is not bad at all. A little bit is good for lowering pH.

Either way, too much CaNO3 is not a good thing. Have to mixed them with KNO3 and K2SO4.

If you add too much CaNO3, your electrical conductivity (eC) will go up quite fast. Calcium is quite conductive which is detrimental to the plants. Aquatic plants eC is around 600 microsiemens (µS) when grown emersed. Ca can easily caused eC to go over 600 µS while not providing enough N-P-K to the water from accumulation. fish tank usually sits around 200-300 µS, if even. For some plants, even over 200 µS will start causing them to melt and die. The plants you see readily available in the fish store can tolerate higher eC level. The more sensitive rarer plants are more prone to melting under higher eC.

A bit of CaNO3 helps lower the potassium nitrate usage and can be supplemented with potassium sulfate to increase the potassium

If you have too much sulfate in the water, then you can skip Calcium nitrate and go with a different source of Calcium.

As for dosing CaNO3, I cannot help you in the aquariums. I add enough fertilizers in my emersed setup to last the week and then do a flush, so I don't have to top off with water or fertilizers. The levels for emersed setup would be a tad high for inhabitants and a waste of fertilizers for large volume of water.

That being said, CaNO3 works great for low tech setup where fertilizers is added once a week after each water change. I haven't figured out how much ppm of Ca from CaNO3 to used in the formula for daily/bi-daily dosing yet.

The one on aquaticplantcentral is for 13% CaNO3

You can use CaNO3 to raise Ca to 20 ppm. Then use K2SO4, KNO3, KH2PO4 like regular EI dosing.

13% CaNO3, 30 grams CaNO3 would give 20 ppm Ca and 60 ppm NO3.

Break that down equally into how many days you planned to dose on a weekly basis. supplement that with K2SO4 and KH2PO4 to get the EI level of dosing.

This would only work if you do close to 80-90% water change to reset the Ca level.

ADDED: The Ca being boosted isn't the direct caused of plants melting as much as the unstable/rising eC level. If you can add 20 ppm Ca at start and keep the eC stable, the plants would be more happy than adding Ca over time and rising the eC up. When CaNO3 is being used as a regular dosing/top up, electrical conductivity monitoring is more crucial than just normal aquarium dosing.
 
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