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Old 01-24-2023, 12:56 PM   #1
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Exclamation Water Softeners, good or bad?

Hello, I am adding a water softener in my home to help with the lime scale issues that I have, my water is decently hard for being in town. I'll give background, then ask the questions.

I currently house a tropical tank, 20 gallon, 9 assorted danios, a horsefaced loach, and a clown pleco.

I will be upgrading to 75 gallon (minimal) and I am not sure if I'm going to transfer the fish and add more fish, or just start a new tank with African Cichlids.

Currently my fish do fine, I just add water conditioner with my tap water. When I test my tank though, my pH is in the lower 8, and my kH is high up there too.

So I was reading about water softeners and aquariums, and it said it can be good or bad depending on what fish you have, but I did not see much on what type of fish they are recommending and not recommending.

So my question(s):
Has anyone had negative effects from using water from a water softener?
What fish are good & bad when using a water softener?

Thanks for the help in advance!

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Old 01-24-2023, 01:26 PM   #2
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Water softeners work on an ion replacement principal. The resins in the softeners remove calcium and replace it sodium. So its not a just a case of water softeners removing calcium to soften the water.

Generally sodium isnt good for fish. Some people get away with it, some people dont. As you suggest this is down to what fish you have and also how much calcium is being removed from your water and how sodium is consequently being added to the water. Fish that are tolerant of higher salinity would be more tolerant than those that arent.

Rasboras, danios, livebearers and most cichlids are generally more tolerant of salt. But it all depends on your personal situation. If your softened water doesn't taste salty you will probably be alright.

Most water softeners have a bypass, so you may be able to use unsoftened water in your tank same as you always have.
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Old 01-24-2023, 06:35 PM   #3
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What is the GH (general hardness), KH (carbonate hardness) and pH of your water supply?
This information can usually be obtained from your water supply company's website or by telephoning them. If they can't help you, take a glass full of tap water to the local pet shop and get them to test it for you. Write the results down (in numbers) when they do the tests. And ask them what the results are in (eg: ppm, dGH, or something else).

Depending on what the GH of your water is, will determine what fish you should keep.

Angelfish, discus, most tetras, most barbs, Bettas, gouramis, rasbora, Corydoras and small species of suckermouth catfish all occur in soft water (GH below 150ppm) and a pH below 7.0.

Livebearers (guppies, platies, swordtails, mollies), rainbowfish and goldfish occur in medium hard water with a GH around 200-250ppm and a pH above 7.0.

If you have very hard water (GH above 300ppm) then look at African Rift Lake cichlids, or use distilled or reverse osmosis water to reduce the GH and keep fishes from softer water.


Danios, loaches and plecos should not be kept with African Rift Lake cichlids. they come from completely different water and the cichlids regularly attack and kill these fish.

You can soften water with a reverse osmosis unit but these can waste a lot of water in the process. You can make a solar still out of a plastic storage container and a bucket. You can buy distilled water or reverse osmosis water but this can get pricey.


As for water softeners, try not to use them for soft water fishes because the sodium that replaces the calcium damages the kidneys in fish, birds and mammals, including people.
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