# Why do fish die from pH shifts? (need nerdy scientific info)



## cgcaver (Jul 10, 2005)

OK, I've always just wondered about this... when fish die from pH shifts, what about it actually kills them? What is the physiological reason for death? The more details the better, I'd really like to know more about this issue


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## Laith (Sep 4, 2004)

Ah, but do fish really die from pH shifts?  

Unless we're talking about going from a pH of 14 to a pH of 1, I think most of the time what is affecting the fish is a radically different osmotic pressure gradient. For example from very hard water to very soft water (or vice versa). It just so happens that this phenomenon is accompanied by a pH shift as well.


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## BryceM (Nov 6, 2005)

I agree with Laith. pH shifts usually happen as a consequence of other things going on in the tank. pH changes alone _can_ kill fish, but it's most always something else. Like other animals the biochemical reactions that take place inside the cells of the fish require a pretty consistent environment to function well. Enzymes that function perfectly at pH 7.4 (speaking of humans, now), might be 100 times less effective at pH 7.0, for example.

To maintain a consistent environment (homeostasis), an organism expends energy to pump the appropriate ions in and out of its cells. The blood stream of fish is largely regulated by the gills, which have functions similar to both lungs and kidneys in mammals. If parameters get to far out of whack, the organism simply isn't able to maintain homeostasis and the chemistry behind life's little processes starts to break down.

If the concept of osmotic load doesn't make sense, imagine a human trying to drink seawater. The osmotic load of seawater is simply too high for us to handle. Instead of adding water to our bloodstream, there is so much stuff disovled within it that it actually pulls water out of the blood. Not helpful! Similar problems occur in the gills of the fish when things get outside of their normal parameters. Some species can compensate for change, but it often takes days to weeks. Some species don't compensate well at all, and require pretty constistent parameters.


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## taekwondodo (Dec 14, 2005)

As a fish moves around a river, it doesn't stick just a fin into a tributary to test the pH difference, the Temp difference, the difference in salinity/hardness - the whole concept _generally_ (IMEAHO) is hogwash.

What kills a fish when moving from one tank to another is more related to the quality of the water. If you have a low pH and nitrites, you have a high concentration of Nitric Acid. If you have a high pH and ammonia, ammonia starts becoming leathal (exponentially) from 7.0 and higher. Either of those are killers.

Have no Ammonia or Nitrite, and you're not moving a fish into an extreme pH range (high CO2 in a pH of 4-5, or significant base in a pH of say 8.5-9 or more) you should be fine.

When I bred discus and angels I used to use drip accumulation until I learned this from the people at the shedd aquarium - after learning this I just moved them from the breading system (pH 4.5-5.0) to the growout system (pH 7.5+) with the net-and-dump method and never lost a fish (or saw any related stress - fish ate food within minutes of being moved). Granted my water quality in both systems was impecible .

- Jeff


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## cgcaver (Jul 10, 2005)

OK, well the main reason I ask is that when I do large water changes 75%-90% (very rare) to do a complete tank cleaning (usually due to an algae take over), it's always very hard on my smaller fish.

I keep the fish in a bucket of tank water then try to slowly reintroduce them to the clean water in the refilled tank by pouring in cupful at a time slowly.

In the past, I've had neon tetras die even when I did a 30% water change. And now my cory's have died as a result of my huge tank cleanout & water change last night. Usually, they are dead, or on the brink, even 15-30 mins after they are put back in the tank. However, my oscars, JDs, etc have always tolerated the water changes OK. On complete changes, they sit at the bottom and stay still for about 4-6 hours, but after that, they're back to normal.

What I don't really get is where the huge change in water params is coming from. My tap water is very basic, water cant get THAT acidic in my tank (I have no CO2). What do you guys think the problem is? I can't stand losing my smaller fish everytime I do a routine water change, and even when Im forced to do a complete tank teardown/clean/refill.


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## banderbe (Nov 17, 2005)

To get to the other side! [smilie=b::heh:[smilie=b:


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## hoppycalif (Apr 7, 2005)

When you do a large water change you may be adding a large amount of ammonia from the chloramine the water company adds to the water. That will kill the fish. You have to be sure to add a neutralizer, such as Seachem's Prime to neutralize the chlorine and ammonia as you add the new water.


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## cgcaver (Jul 10, 2005)

hoppycalif said:


> When you do a large water change you may be adding a large amount of ammonia from the chloramine the water company adds to the water. That will kill the fish. You have to be sure to add a neutralizer, such as Seachem's Prime to neutralize the chlorine and ammonia as you add the new water.


thats actually a great suggestion... Ive often thought our tap water smelled a lil "ammonia'ish". I use cheap de-chlor stuff from walmart, but i'll invest in some seachem goodness


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## taekwondodo (Dec 14, 2005)

sounds like a problem with what's in the TAP.

When I used to fill right out of the tap (like you) with any measurable change, my fish would just drop to the bottom of the tank and if I didn't get them out they would die.

Sometimes it's ammonia/chloromines (as it was for me in Chicago), sometimes it can even be CO2 (I had a well in VA where the tap was loaded with it).

You can use a neutralizer, but I would run the tap through a carbon block (cheap at home depot) into a container (I use two of those 7 gallon water containers people use for camping - get them at wallmart, etc...) and airiate it for a day or so.

Try that and let us know how it works...

- Jeff


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## JanS (Apr 14, 2004)

cgcaver said:


> What I don't really get is where the huge change in water params is coming from. My tap water is very basic, water cant get THAT acidic in my tank (I have no CO2). What do you guys think the problem is? I can't stand losing my smaller fish everytime I do a routine water change, and even when Im forced to do a complete tank teardown/clean/refill.


What are the differences in parameters between the tap and the tank water? If it's getting driven down by itself in the tank, there has to be something causing it, like something decaying, certain rocks, driftwood, etc.
I agree, way too much stress is put on pH since fish are pretty adaptable, but you want to make sure there isn't something in your tank that is altering more than the pH.

I've seen more fish die on water changes from adding different temperature water, or using contaminated equipment.
As mentioned before though, I'd check the source water first, because that very well could be the culprit.
We don't want you to get soured on water changes...


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## BryceM (Nov 6, 2005)

Yep, if your water company uses chloramines instead of regular chlorine it'll be murderous on your fish. It quickly turns into large quantities of free ammonia. A few communities do use it, but most use regular chlorine. A quick phone call to the public works department should answer this question. You really need a good quality water conditioner to take care of this.

I'd say certain fish are more adaptable than others. You can do just about anything you'd like with zebra danios and they simply won't die. I'm pretty sure goldfish can live in Windex. Some tetras can be pretty sensitive though.

Just for the record, I think you can also get into trouble when introducing fish into tanks with quite high CO2 levels. I don't know if it is an embolization effect (bubbles coming out of solution within the bloodstream, causing small blockages of blood flow), or just what exactly, but I've seen it more than once.

Why do a 95 or 100% water change? You can do it if your tap water is similar to what is in the tank, but why bother?


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## taekwondodo (Dec 14, 2005)

guaiac_boy said:


> I'm pretty sure goldfish can live in Windex.


Now I am not so sure about the windex... *but have seen video proof that they can survive for a period of time in electrified Mountain Dew!!!*

eace:

:fear: :bolt:


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## Mnemia (Nov 23, 2004)

I think this is an issue with the tap water too. My water company only uses regular chlorine for disinfection, and I did 50% water changes with NO water conditioner whatsoever for a long time, with no visible signs of stress in any of the fish. They did tell me that they sometimes will send "pulses" of chloramines through the system if they detect any contamination in the system though, so I now use Prime just to be safe.


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## JanS (Apr 14, 2004)

taekwondodo said:


> Now I am not so sure about the windex... *but have seen video proof that they can survive for a period of time in electrified Mountain Dew!!!*
> 
> eace:
> 
> :fear: :bolt:


I think that topic needs a rest, or better yet, a burial.... It has no practical purpose for any responsible aquarist, and could be confusing to a beginner.:yield:

As guaiac_boy said, some fish are much hardier than others and _can_ live in many less that ideal situations, but why do it when we know better?


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## cgcaver (Jul 10, 2005)

I said I had to do a full water change because I was breaking down and thoroughly cleaning out my tank due to massive green spot algae takeover


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## DataGuru (Mar 11, 2005)

I think most large cities are using chloramines now because they create less disinfection biproducts that cause problems for humans.

With pH of 8.2 you don't have much leeway in terms of ammonia levels cuz most is in it's toxic form. At tropical temps, even .25ppm is getting close to toxic levels and .5ppm is at toxic levels. Here's some info I put together on ammonia toxicity, pH and water temp.

I have a lot more ammonia that that in my tap water after it's dechlorinated.


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