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Old 10-12-2011, 10:17 PM   #1
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gH lower than kH in soft water??

Hey everyone.

Just a quick question. I got my API hardness kit. I don't know so much about water chemistry but I know enough to match the test numbers with what my fish need and the following would be nowhere close.

Soft water I get from my father measured low gH, around 30ppm. The kH though was @ 150ppm. The water is softened with potassium rocks.

These are not favorable measurements, I donnot believe, for keeping the fish I have, livebearers. They may not be favorable for any fish.

I'm considering using tapwater, soley, which measured GH 250ppm & KH 150PPM--much closer to where I'd want my water to be.

I'd thought that using soft water and adding hardness would be a better way to go in that I could put a nice combination of minerals of my choosing and not worry so much about the ammonia, chlora's, and metals of the tap water. The soft water reading from the test kit leaves me uncertain of how to do that. I had been planning on using a combination of marine salt mix, epsom, and baking soda in proportions.

I guess mostly my question would be: what is responsible for the funny reading? I would venture to guess it has something to do with something in the soft water not being measured by the KH test, but this may also not be the case.

My tank parameters are well, including a fairly healthy hardness reading, bit low maybe, of gh 160ppm & kh 110.

Anything to shed light on the afore would be much appreciated.

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Old 10-13-2011, 02:54 AM   #2
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GH measures Mg and Ca, which are not the only cations in water. It sounds like for whatever reason you have a lot of another cation (probably sodium) in your water.

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Old 10-13-2011, 09:06 AM   #3
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Fish can adapt to your PH/hardness etc, even though they might prefer a certain type of water they like stability more. Trying to add chemicals and compounds to adjust those levels is asking for trouble, I think. Most people don't know the GH/KH of their water and their fish are fine. As long as PH remains stable and you don't have any fish issues, you may just want to leave it alone.
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Old 10-13-2011, 03:29 PM   #4
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When you use a potassium salt to soften your water, what you are doing is replacing magnesium and calcium with potassium ions. Since GH is a measure of only Mg and Ca, the water is techincally softened. However, the TDS of your water is not changed, and neither is the KH. Soft water fish are used to a low mineral environment, which is not what potassium/sodium softeners create. So using that method won't help your fish at all. Infact, it creates unnatural conditions, since K/Na are not the major cations in normal freshwater. Just use tap water. Most fish are hardy enough to adapt to tap water conditions, and your tap params are fine. Unless you have some sensetivde species, there is no need to soften the water. If you did want to truly soften, you would have to mix tap with RO water, or add minerals back to pure RO.

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Old 10-13-2011, 05:12 PM   #5
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pH & Hardness

Hello ae...

The technical analysis of your tap water will sound like a chemistry lesson. If you're not keeping rare species of fish, the best thing you can do to ensure the success of your tank is to treat the tap water for chlorine, chloramine and ammonia and don't worry about pH, hardness or any of the rest of those things. It's a waste of time. If you try to change things you think are a problem, you'll really hurt your fish.

You have a simple job, replace half the tank water weekly with treated tap water and service your filter. The fish and plants will adapt, they've been doing it since the hobby started.

Just one old "water keeper's" opinion.

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Old 10-13-2011, 07:40 PM   #6
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thank you for your replies.

you seem to have confirmed what i learned through a bit of investigation last night. and that is very good news, thanks again.

ballpark, i thought the problem may have been the potassium not being measured and that would mean the calcium-magnessium, good fish minerals, i've read, not being there because of the softening process. as i said, i had hoped to use a pure water and add amounts of something like a cichlid salt mix, even if in lower proportions, for my livebearers thrivalence. and i may still do this. the fish have seemed ok with the combination i've been using--conditioned tap and softened water--but ok is not what i've been aiming for and/or prefer.

i changed a bit out last night and replaced it with the tap water, about 5 gallons. i hope that if i do this once or twice a week for a few weeks conditions will have become more favorable, and the change in water profile of the mini changes will not stress the fish(the platys seem particularly sensitive), too much.

thanks again.


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