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Below is an e-mail letter/question that I received recently. It seemed to indicate a problem with water softeners, but the problem may be more complex.

I built a house in the country and have my own well. The water was very high in iron so I have a water softener. In the eight years I have lived here my plants in my 125 gallon aquarium just are not doing as well as when I lived in town.

I use oyster grit in my filters and inject CO2 in my tank. My pH is around 6.8-7 (although water from my tap is acidic 6.2-6.3), aquarium KH is about 4, GH 6-7. I add Flourish and Flourish with iron as well as Excel and add Epsom salts and salt substitute but my plants are just not thriving. I have a twin bulb VHO light, on at 10AM, off at 10PM.

I don't over feed and don't have a lot of algae, but there is some on the Vals and Java ferns.

I don't recall you covering water softeners in your book, but it seems to me that I read somewhere that water softeners may add some salinity to a tank when doing water changes.

Is that true and what can I do? [from Lee in Lynden, WA]


My Response:

Water softeners exchange Na+ for the other cations [Ca++, Mg++, and iron (Fe++, and Fe+++)], so the more cations in your water, the more sodium will be released into the water. Excessive sodium (e.g., salt) could very well inhibit plant growth. However, the inhibition could also be due to all those chemicals, which are also "salts", that you are adding to make up for the softened water.

Perhaps, you could try using your well water before it is softened. Maybe, run a hose from a garden outlet to fill your tank? I use well water right out of the tap with few problems and much less work. I am guessing that the "excessive iron" in your well water would not create a problem in your tank. That's because the iron would quickly precipitate out of the water to form iron oxides, and therefore, become totally harmless. I suspect that the objection here to "excessive iron" is its tendency to stain porcelain sinks and bathtubs, not for any toxicity to fish, humans, and plants.
 

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Diana, would it be any better to use potasium chloride in the water softener rather than sodium chloride? KCl for softeners is readily available, but more expensive than NaCl.
 

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Way better indeed. The level of potassium which will cause any problems is way higher than that of sodium. But it will be an expensive solution...
 

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Discussion Starter · #4 ·
I agree. KCl (potassium chloride) would be far better for plants than NaCl. However, it did not seem relevant in this situation, particularly in dealing with a household water softener.

That said, for a small water softener dedicated to planted aquaria, I would use KCl. I mean if you are going to all the trouble and expense to soften water for your planted aquarium, you might as well do it right. :rolleyes:

Thanks for bringing KCl into the discussion!
 

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Haha indeed! And I agree about the excessive iron. 10ppm will do no harm, can't imagine it getting higher unless there are chelators in the well as well;)
 
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