# Reconstituting RO Water



## andy485 (Aug 19, 2005)

I really don't have to use RO water in my tank but I am getting some practice before I spend the money on a salt water setup. Right now I am mixing 50%RO to 50% tap water. I would like to switch to 100% RO water but I have a few questions:
1. Is there any negative effect on fish or plants by using baking soda to raise the KH of 50 gallons of RO water to 4? (like the added sodium) 
2. I have a place to purchase calcium carbonate but have read that it is very slow to dissolve and I have no formula on how much to add, any help with that?
3. What about pottasium carbonate where can I purchase that and find a formula to use?
4. If I dose to the recommended levels of Mg and calcium on the fertilator and use plantex B is this enough to remineralize the RO water?
5. Last but not least what about the electrolytes? How do I reconstitute them or does raising the KH and GH take care of that?


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## Salt (Apr 5, 2005)

*1. Is there any negative effect on fish or plants by using baking soda to raise the KH of 50 gallons of RO water to 4? (like the added sodium) *

_Most people will say no. However, I prefer to use potassium bicarbonate or potassium carbonate to raise KH as I would rather not add the extra sodium cations to the water._

*2. I have a place to purchase calcium carbonate but have read that it is very slow to dissolve and I have no formula on how much to add, any help with that?*

_Put the calcium carbonate in a 1 liter or so container and stir it as much as you can. Add it to the aquarium when your CO2 is switched on. If you have good flow in the tank, the flow will prevent the calcium carbonate from precipitating. The carbonic acid in the water from the CO2 will turn the calcium carbonate into calcium bicarbonate, which *is* soluble in water. My CaCO3 dissolves clear in about 30 minutes and 100% crystal clear in 2 hours maximum.

One thing I do to speed dissolving even more is I use a magnetic stirrer and inject CO2 into the container using my 5 lb reserve CO2 tank and a small Sweetwater fine pore airstone. It does not dissolve all of the CaCO3, but it helps speed it along after adding it to the tank.

Formulas (assume 100% pure chemicals, 100% pure RO/DI water, & a static environment):

Add *9.45332 mg* of CaCO3 to raise calcium 1 ppm in 1 gallon, or *67.56201 mg* to raise calcium 1 dGH in 1 gallon.
Add *6.31357 mg* of CaCO3 to raise carbonate 1 ppm in 1 gallon, or *67.56201 mg* to raise carbonate 1 dKH in 1 gallon.

This is a starting point. Use a GH and/or calcium test kit and a KH test kit to verify your results. There are a lot of dynamic things going on inside a planted tank, and you may have some other calcium sources. I use the Lamotte kits. These kits measure everything in a CaCO3 equivalent. This is why the same amount of CaCO3 raises both the GH and the KH by 1 degree.

I recommend a gram balance (scale) to measure. You can find them on eBay. My scale of preference is the Ohaus Scout Pro 200 gram portable balance. Balances need calibrated. The scale I linked uses a 100 gram and a 200 gram calibration mass._

*3. What about pottasium carbonate where can I purchase that and find a formula to use?*

_You can use either potassium carbonate (K2CO3) or potassium bicarbonate (KHCO3). Potassium carbonate adds more potassium when raising the KH.

There are various places you can probably find it but I purchased mine from Sciencelab.com.

Potassium Bicarbonate, ACS grade ($142.82 / 2.5 KG)
Potassium Bicarbonate, FCC grade ($75.62 / 2.5 KG)
Potassium Bicarbonate, USP grade ($119.33 / 2.5 KG)
Potassium Carbonate, FCC grade ($60.10 / 2.5 KG)
Potassium Carbonate, Purified ($40.77 / 2.5 KG)
Potassium Carbonate, ACS Grade ($177.05 / 2.5 KG)
Potassium Carbonate, USP Grade ($99.18 / 2.5 KG)

Any grade should be fine. The cheapest should be fine. Personally, I use ACS grade. It's a matter of personal preference.

Formulas (assume 100% pure chemicals, 100% pure RO/DI water, & a static environment):

Add *6.31535 mg* of KHCO3 to raise carbonate 1 ppm in 1 gallon, or *67.58110 mg* to raise carbonate 1 dKH in 1 gallon.
Add *7.13233 mg* of KHCO3 to raise potassium 1 ppm in 1 gallon.

Potassium and calcium have very close atomic weights, so the carbonate measurements are virtually identical to CaCO3. KHCO3 raises potassium by 6.97221 ppm for every 1 dKH increase.

Add *8.71812 mg* of K2CO3 to raise carbonate 1 ppm in 1 gallon, or *93.29333 mg* to raise carbonate 1 dKH in 1 gallon.
Add *6.69038 mg* of K2CO3 to raise potassium 1 ppm in 1 gallon.

K2CO3 raises potassium by 13.94440 ppm for every 1 dKH increase.

This is a starting point. Use a KH test kit to verify your results. Most people don't test for potassium, but Lamotte makes a pretty accurate test kit for potassium. It requires bright light, RO water, and a white surface to hold the test tube over. I don't know of any "add to cart" sources for it, but Clarkson Lab will be able to get you one if you want it. You'll have to e-mail them your order request._

*4. If I dose to the recommended levels of Mg and calcium on the fertilator and use plantex B is this enough to remineralize the RO water?*

_Yes. There was a discovery made by Edward that some plants (like some rotallas) will stop growing if the magnesium levels read 43 ppm or more on a test kit. Magnesium levels are taken by doing a GH test and subtracting a calcium test. Rather than using a ratio, I have lately just tried to keep the magnesium levels at 20 ppm (as CaCO3 on the test kits) or less.

Plantex CSM+B is a trace element mix, which I consider more of a fertilizer than a RO reconstituter._

*5. Last but not least what about the electrolytes? How do I reconstitute them or does raising the KH and GH take care of that?*

_An electrolyte is a substance containing free ions which behaves as an electrically conductive medium. So yes, KH and GH takes care of that._


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## Laith (Sep 4, 2004)

I was just about to refer you to Salt as he seems to be our resident expert in using 100% RO water  . But he beat me to it...

Of course, you could just use sodium bicarbonate to raise KH and a product such as Seachem's Equilibrium (or Greg Watson's GH builder) to achieve similar results (yes, perhaps with a bit more Sodium than Salt's method but I've never seen issues with this).

Both methods work. Salt's method probably gives you more exact control, if that's what you're looking for.


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