My Fish Died After Adding Demineralized Water - Why ?

pitAlex

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Hello all,

I just had an unfortunate accident and my beautiful red betta fish died after adding demineralized water. I read that you can use demineralized/distilled water to reduce water hardness which I added to my 30l tank after finding out that my GH levels where near the high limit after being a way for week. So I went and bought 2l of demineralized water and added in the tank. Just 3 hours later I found my poor fish dead - why ? I found numerous posts.. everywhere it says to use such type of water to reduce the hardness and it killed my fish...what happened ??
 

MrBryan723

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You did it too fast is my guess. Stable parameters are better than large swings in water chemistry. Sorry for your loss.
 

ystrout

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That's very strange. I'm going to go with coincidence or there was chemicals/chlorine in the water.

Changing 7% of the water from tap to RODI shouldn't impact the fish at all. GH/KH or PH wouldn't be affected enough for the fish to even notice. And unless you put boiling water in the tank, there wouldn't be enough temp fluctuation for the fish to be affected.

Since you're a new member, we have to ask... Is your tank cycled? It may have died of ammonia poisoning and been a bad coincidence.

Either way, I'm sorry for your loss
 

MrBryan723

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That doesn't matter. Dying of osmotic shock would take a lot longer than being under a waterfall of RO water.
While true, shock doesn't take very long. I agree that such a small amount of distilled water shouldn't cause a fish to die, but I really doubt it would be chlorine or chemicals as a cause. Uncycled maybe, but doubtful as well because adding clean water in the tank should reduce the ammonia. Granted it could be a long standing problem where the fish was already suffering from ammonia poisoning and the little swing in Parameters just did him in.
 

Cognac82

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I am sorry about your fish. That is very sad.

Any change in water chemistry is difficult for a fish to deal with. The osmoregulatory systems of fish are extremely complex. Any wild swing in any part of water chemistry is the equivalent of stepping off an airplane at a high altitude when you are used to living at sea level and then trying to run a marathon. You would die. This is likely what happened to your fish, especially if you changed all of the water at once and especially if it was a different temperature as well.
Just a question. Why did you feel like you needed to alter the hardness of your water? I have two bettas and they're not the first ones I have had, others living past five years of age in a pH of 8.0 and a GH and KH of 12 and 8.
As mentioned before, stable water is better than "ideal", especially if you can't maintain it.
This is a great place to learn from people who have kept fish for a great many years in a wide variety of water conditions. Don't give up. Do a little research and ask some questions and you can get another betta to enjoy. This is a rewarding hobby, even if it is frustrating at times.
 
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pitAlex

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This is a mature tank - I had the fish for over 8 months. Fish was very active and healthy, I use all conditioners for the water and I do regular maintenance. It also has plenty of plants in it.

The GH level was at nearly the last level under the test color marks (it say >21*d) and I had 2 nerite snails in there which I found dead right after I came back from vacation. The fish didn't show any problems though. So...seeing the snails dead and seeing high GH got me thinking that I should try and remedy this.

Btw the parameters didn't change...well you could say it went from 20 to maybe 18 judging from the color strip... but its a very slight change in color.

Speaking of fish keeping I do have another 60l tank with another betta, 4 cory and 4 ottocinclus so I still have "little friends" to look after. It just so weird this happen. Its true that lately I kept my eye on the bigger thank most of the times, but that doesn't mean I wasn't looking after him as well. So I don't know how the gh levels got so high and why after doing this..he died.

Only thing I can think of right now is that the water was not in fact demineralized. That is was counter-fitted or gone bad, something that made it be poison instead.

This is what I used (maybe I used the wrong product?) :

Apa demineralizata Pouce 5 L - Auchan online
 
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pitAlex

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A second question I have now : Do I need to clear out the tank, remove all the water, clean the plants, change the gravel etc before I can add a new fish ?
 

MrBryan723

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Well, if you think it was a contaminate it might not be a bad idea to at least do a few water changes on it. I doubt you'd have to remove the plants or gravel tho. Just a good rinse of everything.
 

david1978

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I can't see adding 2 l of water of any kind to hurt anything in a 30 l tank. Heck that's even a good rain storm. Some people don't even bother to dechlorinate when they just top a tank off since its so diluted. If the bag was real old it could be a contaminate from the package. Like bottled water the expiration date isn't for the water its for the bottle it comes in.
At this point I would just do as big of a water change as you can and refill it with tap as you were doing.
 
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pitAlex

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I guess what happened, happened... Thanks for your inpur guys I will procced in doing a full watet change on the tank.
 

Skavatar

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The GH level was at nearly the last level under the test color marks (it say >21*d) and I had 2 nerite snails in there which I found dead right after I came back from vacation. The fish didn't show any problems though. So...seeing the snails dead and seeing high GH got me thinking that I should try and remedy this.
but what were the KH carbonate levels? too low and the pH will crash, b/c the nitrogen cycle produces acids.
 
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pitAlex

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KH never changes, it always between 3* and 6*, right in the middle of the measurement color.

PH is at 7 even now.
 
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