Well water and changing parameters


Fish Aficionado
Dec 31, 2004
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My house was built in 1961 by my parents. We have had our own well since day one. In the earlt years folks who came to play tennis on my dad's court commented on how great our water tasted.

fast forward to the start of 2001 and i am setting up my first aquarium. Onc I learned enough to be able to understand parameters and how to measure them, my well water was as follows:
pH at 7.3 The water came from the tap loaded with CO2 which caused and initial reading of 6.3 until the excess CO2 out-gassed.
KH at 4-5 dg
GH at 5-6 dg.
Estimated TDS of at least 106 ppm or somewhat higher.

Once I began ramping up due to MTS I got into breeding zebra plecos, nice woman who became a buyer and friend used to come by with a bunch of 5 gal. buckets to take some of my tap water for her tanks. One day she stuck her TDS meter into one of my tanks and when done asked if I realized my tap water was 83 ppm. Of course I said no it wasn't, it is about 106 or a bi higher. So she retested and showed me the result.

After she left I retested all the params and got this
pH 7.0
KH 3 dg
GH 4-5 dg
TDS 83 ppm (I had purchased my own TDS meter).

I had no issues with the changes as my fish seemed to love my well water. And then we hit a period of repeated very heavy rains over a week or 10 days. I was still regularly testing for tap and tank TDS and was amazed when I discovered my tap had dropped to 53 ppm. All the rainwater hitting the aquifer had caused the TDS to drop. But over time it worked its way back to 83.

Fast forward to today. Over the years I had gotten into keeping Altums and their tank started at 4.2 pH with TDS between 20 and 30 ppm. Over time it was raised to 6.0 - 6.5 pH and the TDS were targeted at between 50 and 60 ppm. I had bought an RO/DI unit to make the pure water I had to mix with my tap to hit my targets.

Lately I have noticed that after I do water changes on the altum tank the way I have done them from the start, the parameters start to drift up t0o fast. Normally, over a week between changes the TDS goes up about 10 ppm and the pH moves towards 6.5. I normally change 40% and I pre-batch to needed params in a Rubbermade garbage can next to the tank. Yesterday, after a water change the pH was 6.0 and the TDS were 60. Today the reading was 6.6 and 70ppm. So I finally decided to check my tap. I have only done the TDS so far, it was 99 ppm. I will do the pH later.

Over the years when the area has had drought conditions and we overuse the water, as in adding to the pool or watering the lawn that the water will start to run brown. Sediment gets into the water because the level a few 100 feet down is not coming back up fast enough. We recently had two episodes of this in the past month.

Clearly my tap water params have changed yet again. So far my fish are doing fine and spawning as much as ever. But, the Altums are more sensitive and I will need to make some changes. I am ay an 11/9, RODI/tap. I think I need to make that 12/8.

My point here is that folks who have their own well water should test their parameters over time as they are more likely to change than those one sees from a municipal water supply. Given the climate we are seeing with exreme droughts and dangerous flooding being the rule rather than the exception, this testing is more important than ever. I am thinking even mnunicipal supllies may not be immune to such changes.


Fish Herder
Oct 14, 2011
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Eastern Canada
This isn't just a well water issue. In my old house, there were seasonal variations in the tds, from 75 to 110.


Fish Crazy
Jan 14, 2021
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It sounds to me like you may have a fairly shallow well. Do your folks know how deep it is? I am on a well, but seasonal variations in rain, temperature, etc. do not change what it coming out. It's 173' deep. Depth provides not only supply, but stability (often, but there are exceptions).

Not that knowing your well depth will change the variability, and that you are having to test more regularly. Were I in your shoes, I might try to figure out how I could hook up a float valve to a tank that is far larger than I need for any given water chance. This would allow the CO2 to off-gas, as well as create an averaging effect for any variations you are experience from the well, decreasing the impact on your tanks and their inhabitants.

Or drill a deeper well. ;)

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