Water changes

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Geochurchi

Feeder Fish
MFK Member
Jul 9, 2021
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Hi All , changed water this AM checked water in tank and water to be added, with in 6 hours all 3 Cichlids were dead, this has happened before 3 or 4 times, 12 Gal tank changed about 4 1/2 gals.
Any thoughts?
Geo ??
 
Did you add something to get rid of the chlorine in the new water?
 
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What kinds of cichlids? How big?
What is your water like? Did you put anything in the tank? Sound like there was some chemical that got in.
 
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Hi, tank has been set up for ever, added water tested the same as water in tank, this is not the first time this has happened, I take water samples to Petco for testing, and all is well there, these were 3 heathy Assorted Cichlid’s in tank from April, tank is always crystal clear.
Geo??
 
Make sure to use a water conditioner that neutralizes chloramine as well as chlorine.
Be sure to dose the prescribed amount of water conditioner.
 
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The tap water may be tainted with a chemical water tests cannot detect. For example, synthetic substances (eg: plastics) toxic to fish.
 
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How long between water changes?
The reason I ask, is that in such a small tank, water parameters could drastically change in only a week.
And the new water could be quite different, than the old.
In such a small tank, pH could crash in only a few days, and if the new water is pH 8, but the tank water has crashed to a pH of 5, this is enough of a shock to cause serious stress in some cichlids.

Another thought is gas bubble embollism.
If your source water is cold, it can be super saturated with gases in the pipes, under pressure.
When new water is put in the tank, those gases are suddenly released, and can cause embollism (killing fish).

And as others have suggested, are you dechlorinating the newly added water?
If I were you, I'd get a test kit, or strips (with a chlorine option), and test tap water, tank water before and after every water change for a while.
Don't rely on simply going to a LFS occasionally for that kind of important info. Its something you should always be aware of, as a fish keeper.

And if you draw a glass of water, and its cloudy with microscopic bubbles, clearing from the bottom up, this means it is saturated with gas, so letting it sit a while until those bubble off gas before adding to the tank, just might help.
I do 30-40% water changes every other day on my 300 gallon system, and have never lost a fish due to a water change.
 
Does sound like the water change is killing your fish. Look at the whole problem, what things were the same last time you killed fish?

Are you using contaminated buckets? Are you flushing hoses/pipes to clear old water, do you need to clean your hands?

What percentage of water is changed. What is your water source?
 
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