# Total loss of fish when changing water :(



## sendthis (Dec 15, 2010)

okay, so I know -why- my fish died. I must have a lot of trapped junk when raised the ammonia level, trapped gases, or releasng a lot of anaerobic bacteria from the gravel.

My question is, what is the best way to avoid it in the future?

I had a pretty heavily planted tank, no CO2, and my nitrates/nitrites/ammonia were always zero. So I actually didn't change the water for 3 months.

So I did a massive WC one day and I guess I disturbed so much of the bottom ... 

1 ) In the future, should I do more smaller WCs and disturb small portions of gravel at a time.
2 ) Just do WC without disturbing the bottom
3 ) Remove fish?

The purpose of the WC was to get rid of the junk all at one go... although the tank was pretty healthy without it. I did need CO2 as BBA was starting to take over and I was controlling it with Excel.

Even as I type this, I'm kind of thinking I know what I need to do ... but wanted to confirm.

Thanks!


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## Zapins (Jul 28, 2004)

The best way is to do weekly water changes.

Are you sure you neutralized the chlorine/chloramine when you add he new water?

Also if there is a lot of waste in the tank and there is a large pH change (from the freshwater) it makes the ammonia more toxic thus killing the fish. 

The best thing is not to let the wastes build up to that point. But if it does you should do small water changes many times over the course of a week or two in order to remove the ammonia and not shock the fish.


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## sendthis (Dec 15, 2010)

Zapins said:


> The best way is to do weekly water changes.
> 
> Are you sure you neutralized the chlorine/chloramine when you add he new water?
> 
> ...


Yeah, I treat for 2x volume of the tank using sodium thiosulfate. So if I do a 30G WC, I put enough to treat 150G in my 75G aquarium. I use the same technique in my BB tank and the fish never have had a problem. I also used this prior to adding plants with the same same fish that died with no problems.


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## obie (Mar 28, 2011)

I dont vacuum my gravel when I do a waterchange. I settle 4 gallons of water in jugs two days previous from my dedicated WC day (saturday), so that the water will be room temp too. gravity feed 4 gallons from the aquarium to a bucket, and pour the new 4 gallons in. None of my fish have died in a long long time, and one of my female platys had her second batch of fry on friday, so I guess I'm doing something right.


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## Tex Gal (Nov 1, 2007)

How long did it take for all your fish to die? Was it within minutes or days? If it was within minutes it sounds like you had something in the water which you put in. If it was overnight or days sounds like was a change in the TDS from the old loaded up water and the new water. If you don't change your water for a long time you can get a lot of Total Dissolved Solids accumulating in your water since water continues to evaporate and we just keep topping off the tanks. So when you do a water change (huge) you are taking out all the higher pH water and replacing it with lower pH water and the fish can't handle a change that drastic. 

If you really disturbed the substrate it could be ammonia, but then it doesn't have anything to do with the w/c. It would be about disturbing the substrate and releasing ammonia. A water change would only HELP in that situation.

It makes me think you either had something in the new water that you didn't know about (a city additive or something) or you drastically changed the pH.


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## jetajockey (Nov 11, 2010)

i've heard of people doing a heavy gravel vac or substrate change and wiping out fish. Apart from the possibilities already mentioned above, the only other thing was possibly a release of a large amount of trapped gas.


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## ddavila06 (Jan 31, 2009)

i do massive water changes in a regular basis...50% or more every two three weeks. i disturb the soil pretty badly on a regular basis as well...moving plants, replanting, organizing, getting rid of stuff...could teh dechlorinartor be bad maybe? did you loose all r most fish? sorry for ur loss...


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## Fangeo (Apr 30, 2005)

I have never seen trapped gasses in a planted tank kill fish but I suppose it is possible. I have seen this happen with marine tanks, very often with newbies to the reef hobby.


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