2 Year Old Betta Died Suddenly - After Water Change

[Mammabe1]

Hello, I need help! This has happened to me several times - I change my betta's water and he is dead the next day.  I am mystified.  I have a betta in a 2 gallon container and change his water every week.  I have done this for 2 years and he has lived there happy and healthy, quite large and full finned and very responsive and always swimming around or in and out of his cave.  I always keep a few live plants in the tank.  After his water change today, I put in the dechlorinator as per usual but this time he died only a few hours after the water change.  This happened to another betta I had for about 6 months, then after one water change, he was dead the next day.  The only thing I can think of is my water softener - does anyone know if that would make a difference?  I mean, when you first add salt to the water softener, there may be a higher concentration of salt in the water than when it is low or has run out.... Now, actually I also changed the water in my 5 gallon tank in which I keep another betta I've had also for a few years, and he is fine.  So I dont' know - this is a mystery to me.  I am very sad he died and am afraid of doing the next water change on my next betta (I have 8 others).  Any ideas or suggestions would be greatly appreciated.
 
Thank you!

 

[neontetris]

How did you go about reintroducing your fish to the new water? Is it possible that he might have experienced shock as a result of swift change in temperature or water conditions?

 

[PrairieSunflower]

Your betta would benefit from being moved to a cycled tank, you'd be able to do partial water changes once the tank is cycled and that would be less likely to risk shock.
 
Is it possible the salt wasn't fully dissolved and the betta found some in the water and ate it?

 

[Mamashack]

2 gallons is a wee bit small for a betta. Your 5 gallon tank is a much better size as they do like to swim. 
Is there any particular reason you are using softened water? 
Are your tanks filtered and cycled? Do you temperature match your replacement water with what was in the tank previously? Needs to be within 1 degree to be safe.

 

[the_lock_man]

2 gallons is a wee bit small for a betta. Your 5 gallon tank is a much better size as they do like to swim. 
Is there any particular reason you are using softened water? 
Are your tanks filtered and cycled? Do you temperature match your replacement water with what was in the tank previously? Needs to be within 1 degree to be safe.

 
I'm certainly wondering if it's the artificially softened water that's the problem.
 
I don't know how these things work, particularly, but I would imagine that as you get close to needing to recharge the softener, the system is not softening the water as much. Say you do a water change just before adding more salt to the system, it might well be that you are using fairly hard water still. Next week, you've recharged the system, and you have very soft water. If you are doing a decently sized water change (which you would need to if the tank is unfiltered), then the sudden change in hardness could well shock the fish sufficiently to kill it.
 
Mamashack is on the right lines with the temperature thing, too, a sudden change in temp can also shock the fish. The temperature needs to be roughly temperature matched, the 1 degree thing is a little extreme though (sorry, Mama!), a rainstorm in the wild can change water temp by a degree and more quickly, but you wouldn't want to do a change that affected temperature by more than 3-4 degrees, and that would be quite easy in a small tank like a 2gallon. (And I agree that this is really too small for a betta).

 

[Mammabe1]

Thanks all for your comments.  He has lived fine for 2 years in there and yes, I always match the temperature - remember, I have done over 100 water changes for this guy and he died after this one in particular.  I know 2 gallons is not ideal but with proper care, they can thrive in a 2 gallon which he has until this unfortunate day.  Anyway, I was looking for help in what the could be the cause so I could be sure to avoid it in the future or do things differently in the future, not to be criticized on the size of his living quarters.  
 
The water softener is because we have hard water in the town I live in. 
 
Does anyone know if I fill a bucket of water and let it sit for 24 hours, would that help do you think? 
 
Thank you!

 

[Mamashack]

 
 
Does anyone know if I fill a bucket of water and let it sit for 24 hours, would that help do you think? 
 
Thank you!

 
Letting it stand wouldn't make much difference to the hardness unless there's lots of evaporation during that time in which case it may make it a bit harder.
However some chlorine will gas off. Before chemical water conditioners came on the scene that's how we used to dechlorinate water.
 
 

 
Mamashack is on the right lines with the temperature thing, too, a sudden change in temp can also shock the fish. The temperature needs to be roughly temperature matched, the 1 degree thing is a little extreme though (sorry, Mama!), a rainstorm in the wild can change water temp by a degree and more quickly, but you wouldn't want to do a change that affected temperature by more than 3-4 degrees, and that would be quite easy in a small tank like a 2gallon. (And I agree that this is really too small for a betta).
 

I'm not the least offended TLM  

 - that's just what I was told to do and I've pretty much stuck to it. I use my hand to match the temp and 9 times out of 10 it's been within 1⁰ anyway.

 

[fm1978]

Might I suggest using cooled boiling water instead of your water softening machine - it seems like it could have less than consistent results.
 
Also, I noticed you said that you add the water conditioner after the water change, minor point, but, I certainly feel more comfortable adding it to the change water prior to adding it back to the tank.