# Perfect water?



## Yurtle (Jul 31, 2006)

So here is an idea. I have access to all the distilled/deionized water I could ever want. Right at the tank too. My tank is in a chemistry lab. I know using distilled water for water changes is bad for multiple reasons. (no essential minerals, no buffering capacity etc.) I was wondering if I could basically make ideal water from this though. Ideal (from what I have read) conditions for (a low light, lightly planted tank, so no CO2 injection) would be 10 ppm NO3, 20 ppm K, .2 ppm PO4. You could get those with a combination of KNO3 and KPO4 and maybe KSO4 or KCl (for more K). You could dose a comprehensive for trace elements. But I will still have to add something for kH, gH, and pH stabilization. Sodium or calcium carbonate or bicarbonate addition maybe.

Now say I want to change 10 gallons of a 30 gallon tank (33% water change)

5g of sodium bicarbonate in 10 gallons will give a kH of ~100 ppm 
6g of calcium chloride in 10 gallons will give a gH of ~100 ppm

now

15.6 mg of potassium phosphate
616.7 mg of potassium nitrate
and 1.156 g of potassium sulfate (or 990 mg of potassium chloride)
would give 
10 ppm nitrates
.2 ppm phosphates
and 20 ppm potassium. (Assuming the potassium from the potassium phosphate makes a negligible contribution to the potassium concentration, which is a safe assumption)

Now all that would be left would be to make sure that the trace elements are available this could be done through a comprehensive fert. I don't know if a comprehensive fertilizer made for plants (like flourish comp.)would also take care of the traces for the fish or would I have to use something like Kent's Zoe Freshwater. I would imagine that one or the other would be fine.

This could be adjusted so that the fert doses were lower for nitrate and phosphate if you were trying to dilute out already high levels.

Possible problems:
I am not sure what the pH would end up being.
I didn't include an iron supplement for the plants, but I dont think it would be too hard.
I am assuming, maybe incorrectly, that the addition of the ferts wouldn't change the kH, gH, or pH appreciably. Addition of PO3 ions would definitely effect the buffering capacity due to the PO3-HPO3-H2P03 equilibrium. But in such a small amount I dont think it would have a noticeable effect. The sulfate also could buffer with the SO4-HSO4, but if you used potassium chloride you wouldn't have to deal with that. 
There is no magnesium here which is partly responsible for gH. I am pretty sure that magnesium is an essential element for both fish and plants. I know the Flourish Comprehensive fert has magnesium in it but I don't know if it would be enough.

I was just bored, let me know what you guys think. I would make up a small batch and test the parameters right now but I don't have a kH or gH test kit.


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## Piranha Guru (Nov 24, 2005)

I would stick to dosing the tank itself to achieve your desired nitrate, phosphorus, potassium, and trace levels for plants...it's hard enough to maintain ideal levels (too many variables trying to get your change water to have the proper concentration in concert with the rest of the tank water). You can add R/O right, Equilibrium (best for plants), or Electro-Right to get the electrolyte/mineral balance back to where it should be and pH adjuster to get your desired pH. Then you can do all the water changes you want.


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## plantbrain (Jul 3, 2007)

You want 2.0 PO4, not 0.2 PO4 ppms.

Also, for Piranha and Discus etc, treat them the same, you will only wnat a very very light load if you keep them in a no CO2 planted tank.

Why?

Non CO2 planted tanks do not get frequent water changes.
It'll cause algae.

The goal there is to balance the in/out puts.

So you need balanced fish load, high stocking levels, high fish waste production/live food etc= bad combo.

I'd go CO2 or Excel dosing(which would cost a lot over time).

Then you can change all the water you want.

Many simply blend tap with RO/DI to get a decent target KH, say 3 degrees and leave it at that.

GH booster(seAchem Equilibrium b ut 15X cheaper) and baking soda(for KH) are all you might need to adjust GH and KH.

Regards, 
Tom Barr


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