# 50% water change resulted in fish deaths~ help!



## hariom (Sep 2, 2008)

hi guys,
im a newbie from Savannah, GA.
tank parameters:

pH: 7
kh: 8
co2: 24 ppm.
Nitrates: 15 ppm
ammonia and nitrites: 0 ppm. 

i recently had a black beard infestation and hence raised co2 levels and started keeping it ON round the clock. only since last 7 days.

today was a nightmare~~~

did a regular 50% water change and within the next 1/2 hr had 8 fish deaths...2 male large congos and rest conchu blue tetras...after frantically looking for reports and articles concluded OBVIOUS pH change which threw all in shock! and killed them. tap water is around 7.6. and for the last non stop 7 days of injecting co2 my tank pH was close to 6.9. all fish started breathing heavily. some coming up to the surface...jumping floating upside down and then eventually dying...the tetras seem to take the toll. i started injecting 02 (used an air pump to inject into the powerhead) thinking it was a co2 overdose.....because when ever i do a water change, that is the only time i get pearling.

i have always wondered why i never have pearling daily?....like other hobbyists on forums.

now im wondering what the co2 injection schedule should be...and how do i do a water changes now..should i have lights ON or OFF during water changes? lighting increases pH right?

should I go back to my schedule of stopping co2 in the night ??? never ever had this happen before among my 1 1/2 years of doing water changes. i read that co2 should not be shut off in the night as the pH swings so frequently will be stressful to fish....

after almost 5 hrs now ....the 2 remaining female congos are still breathing heavily...others seem to be fine. lights were turned off for the whole time to reduce pH and stress and co2 injection has been stopped.
aerator still running with powerhead. 

please advice on this matter. im tired and upset of this disaster! :rain:


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## surpera1 (Feb 18, 2009)

what is your KH ? if it is 2 or 3 or 4 you are OK - if really low say 0 or 1 - when you crank up the co2 it can cause a PH crash and kill fish - likely what happened - i advise timers for lights , co2 , powerhead diffuser , and airstone . co2 and diffuser on 2 hours before lights on . co2 and diffuser off when lights go off . airstone on at lights off . airstone off 2 hours before lights on . in the daytime plants take up co2 and release O2 , at night this reverses - if you run co2 at night you can kill fish - you also need to tell me what kind of substrate and ferts and lighting and tank size - tap PH , KH , GH , temp , filter , circulation etc - but this kinda stuff has happened to everyone here at one time or another - nothing worse than a tank crashing and losing long kept fish


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## Bert H (Mar 2, 2004)

I doubt the CO2 was the cause of your disaster. If after running it 24/7 your pH is at 6.9, you did not suffer a pH crash. There are folks who run pH down to the low 6's with no problems. And if your tap water is 7.6, I doubt you have kh of 0-1. Of course, all this assumes your pH readings are accurate.

Is this your first water change, or have you been doing them regularly? I assume you used Prime or a similar product properly? Any chance of something toxic having been picked up by your hoses, buckets, etc?

I wouldn't worry about not seeing pearling on a regular basis. Let the overall health of your plants/tank be your measuring stick, not pearling. You may be well aware of the following, but in case you're not, here's a couple of references which you might find helpful:

http://www.aquatic-plants.org/articles/basics/pages/index.html
http://www.rexgrigg.com/

BTW, welcome to the forum!


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## jmontee (Feb 7, 2008)

+1 on pH/CO2 not being your problem. My tap water is pH 8 when it comes out and is 7 after 24 hours. I run CO2 so during the photoperiod my pH is between 6.2 and 6.4 and I have done 70% water changes during this time with water straight from the tap using a Python. In almost all cases the pH is a problem when you have an increase in total dissolved solids or other contaminants in your water. My guess would be something wrong with dechlorinators/water conditioners. A change from 6.9 to 7.6 is really inconsequential unless it has to do with something in the water quality.

Also if you see pearling very quickly after the water change it probably has more to do with increased dissolved oxygen in the new water than increased CO2 in the water.

Did you vac or disturb the substrate that could have released harmful gases into the tank? Could there be some new treatment being done by water management in your area?


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## Quetzalcoatl (Feb 13, 2009)

I agree with rest of the people here that pH is not the source of problem. More than likely you had something left over in the water that was toxic. Did you properly dechlorinate your water? Did you match the temperature? Was the bucket/hose clean? Did you disturb your substrate or filter media during your water change?


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## Tex Gal (Nov 1, 2007)

Also to add to what others have said.... sometimes the water companies will add extra or different amounts or chloramines or other chemicals. Twice in the summer, in dry periods I did a water change and lost some danios. Everybody else was ok but many danios died within minutes. I do waterchanges each week. It was just something that was in the water that week....


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## eco-mod (Oct 19, 2007)

+1 about the water company changing specs. This is probably the biggest time of the year for changes in what they add to the water. I had a bit of a swing in one of my tanks at the plant level due to a change in the water coming from the tap. Definitely use Prime or similar product. The sneaky one is chloromine, at least for me. I try to let my water sit in buckets with any additives for 6+ hours before a water change just as an extra precaution.


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## crystalview (Mar 9, 2008)

I stirred my substrate to much and released anorabic bacteria. Within a 1/2hr everyone was breathing at the top and dead shortly there after. I have always done a 50% wc weekly. My substrate was to deep.



















5


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## bosmahe1 (May 14, 2005)

I wonder if doing a 25% water change would have given you a warning that something changed in water quality before the carnage? Of course, if it was something in the gravel, it probably would have happened regardless.


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## hariom (Sep 2, 2008)

thanks guys for all your comments...had been busy with school to apologize for the delay.

reading your comments...i kinda feel there was something in the tap water. i have been doing water changes every week and never had a problem. 
i don't think i stirred my substrate (eco complete) during the change as i use a python as well. temperature was definetly not an issue as i monitor it during water changes. sometimes i ve had a 6 deg change as well the fish have taken the change well.

today after 7 days i did only a 30% water change and in 2 batches. kept a close eye on the remaining female congos. as soon as they started breathing heavily (or felt like they were), paused the fill and then after 15-20 mins started again. all fish are fine today...

here are my other details:
http://www.emergingintuitions.com/Wordpress blog/?page_id=189

the fish plant blog has the intro details:
while updates are posted under the planted aquarium category.

would appreciate all to comment on it when ever you guys get a chance.


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## Tex Gal (Nov 1, 2007)

I just did a w/c today and saw a couple of catfish in distress. I put a little more prime in and they were ok. I think sometimes the water company puts a little more chloramines in than usual.


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