# Other Aquarium Forums > Fish Care, Nutrition and Water Management >  URGENT HELP! Lots of my fish dead after massive water change!

## equidorz

few days back i decided to do a water change for my tank.
i wash both my cannister and change almost 80% of the tank's water. after which i begin to see my fishes dying one by one. almost 3-5 die everyday. it have been 3 days since my water change. the fish tails seemed to rot and their eyes seemed swollen and pop out. now alot of my swimmin side ways. really need help. please anyone. give advice..

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## joopsg

Hi equidorz, your 1st mistake was to wash the cansiter filter and do massive water change at the same time. why is it so? I assume your canister filter has been used for quite some time therefore the colony of bacteria should be matued to handle the tank bioload. washing the filter means killing the colony especially when you washed it very clean, chlorine will kill the bacteria. Next doing a change of 80&#37; of water will change the water parameters drastically which will lead your fish to suffer from either pH shock or temperature shock. pH shock mean a sudden change of pH in a very short time,; like wise for the temperature. After massive water change and cleaning of filter, your tank should undergo the process of cycling again meaning the ammonia, nitrite, nitrate and other elements parameter will go haywire and the biological cycle have to restart. Your tank should also have an outbreak of bacteria bloom whereas the water is cloudy for days. Once the cloudiness clears, your tanks should be up and running. to overcome these, can try to use those bacteria culture purchase off shelf to jump start your colony. Hope my information helps.

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## Interestor

> few days back i decided to do a water change for my tank.
> i wash both my cannister and change almost 80% of the tank's water. after which i begin to see my fishes dying one by one. almost 3-5 die everyday. it have been 3 days since my water change. the fish tails seemed to rot and their eyes seemed swollen and pop out. now alot of my swimmin side ways. really need help. please anyone. give advice..


next time if this happen again, re-do a 100%WC immediately with good water conditioner.

what fish are you having ?

CHeers..

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## equidorz

> next time if this happen again, re-do a 100%WC immediately with good water conditioner.
> 
> what fish are you having ?
> 
> CHeers..


i havin rummies and cardinals.alot of them dying. the fishes start to turn white and very weak after a while they will die. so is it ok for me to do a 100% wc now? or is it too late? any other better soultions now? im desperate.

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## equidorz

> Hi equidorz, your 1st mistake was to wash the cansiter filter and do massive water change at the same time. why is it so? I assume your canister filter has been used for quite some time therefore the colony of bacteria should be matued to handle the tank bioload. washing the filter means killing the colony especially when you washed it very clean, chlorine will kill the bacteria. Next doing a change of 80&#37; of water will change the water parameters drastically which will lead your fish to suffer from either pH shock or temperature shock. pH shock mean a sudden change of pH in a very short time,; like wise for the temperature. After massive water change and cleaning of filter, your tank should undergo the process of cycling again meaning the ammonia, nitrite, nitrate and other elements parameter will go haywire and the biological cycle have to restart. Your tank should also have an outbreak of bacteria bloom whereas the water is cloudy for days. Once the cloudiness clears, your tanks should be up and running. to overcome these, can try to use those bacteria culture purchase off shelf to jump start your colony. Hope my information helps.


thanks bro for your information. but now i can only wait for the fishes to die one by one until my tank condition is stable. treat it as an experience learned

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## Interestor

do you uses water conditioner ?

for me i would do a 100&#37; WC with added water conditioner and salt.

what medication you had in hands now ?

PP will be the best  :Smile: 

hope yours is not a planted tank.
do a QT process in a bare tank is advice.

CHeers..

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## equidorz

sorry to say mine is a planted. i dont use any conditioner. and what do *you* mean by conditoneR? lol.. and what is pp? the only thing i done is add those powder form bacteria into the canister and hope bacteria will boom. thats is all! anyway really thanks for *your* feed back and advices. thanks bro

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## Interestor

> sorry to say mine is a planted. i dont use any conditioner. and what do *you* mean by conditoneR? lol.. and what is pp? the only thing i done is add those powder form bacteria into the canister and hope bacteria will boom. thats is all! anyway really thanks for *your* feed back and advices. thanks bro


Sorry, spelling error  :Grin:  for conditioner.

Advice you to read up on local water topics.

CHeers...

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## gummynut

what is the reason for you to do a massive water change in the first place? anyway, in my opinion, a massive water change may lead to complications because the entire system is destabilised. your bacteria colonies is being wiped out which could lead to a spike in ammonia level. 20-30% water change is advisable every week provided that the tap water has been treated appropriately.

if you did not use any anti-chlorine solution during your 80% water change, then the presence of chlorine and chloramine are good enough to kill all your life stock. As a quick solution, you could use some carbon media to suck up all bad chemicals. but i guess that the harm has already been done so you could only sit and wait. more water change is likely going to put stress to the fishes further.

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## Jungle-mania

If you have chunks of brown algae and sediments flowing in the water, use crystal clear solutions, it helps to coagulate any floating particles in the water, secondly water conditioner are used to remove chlorine & chloramine. Better ones like seachem prime removes ammonia and nitrate. Ultimately, you still need to top up your bacteria count, they are the most important. Skip the 100&#37; water change, it is too late. It is best you stick to about 30% water change every week.

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## koolman

> few days back i decided to do a water change for my tank.
> i wash both my cannister and change almost 80% of the tank's water. after which i begin to see my fishes dying one by one. almost 3-5 die everyday. it have been 3 days since my water change. the fish tails seemed to rot and their eyes seemed swollen and pop out. now alot of my swimmin side ways. really need help. please anyone. give advice..


Hi bro

Your greatest mistake is that you change 80% of your tank water. You have remove those good bacteria in your water. I think that you are experiencing PH burn that cause your fish tails to rot. You must not change anymore water. You need to bulid BB in your water. If you have good filtration, you just need to change 25% of your water weekly.

Cheers

Koolman

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## equidorz

okok thanks to all of you ppl for your feed back and advices. but since my first move was a mistake and there is already no return. just have to learn from my mistake and hopefully my tank will become stable asap. now i just scoopin dead fishes when i get home.sad man. the tetras with me for 1.5yrs already. will go buy some water conditoner tml after work.

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## barmby

Plantas owner once said " what if you walk out of your house and it is suddenly winter ? " Will you fall sick ??

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## AA24

if you are still trying to save your remaining fish.. 

put them all into a bare tank.. fresh water with conditioner .. 30&#37; water change everyday.. (very work intensive sorry).. till your old tank is cycled.. hopefully it will not be too long.. but you are loking at 4weeks minimum.. best of luck..

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