Post Mortem - What The Heck?!

[jdubs]

Hi,
 
I have a 10 gallon fully cycled tanl (fishless cycled)  I had 5 ember tetras (approx 3 years old) and 2 dwarf rasboras (under a year) and about 10 cherry shrimp.  Last night all was well fish and shrimp acting normal.  This morning ALL the fish were dead!  All the shrimp are alive.
 
Parameters are as follows:
 
Ammonia 0
Nitrite 0
Nitrate <5
PH 6.4-6.6 (same as usual)
water temp 76F
 
The only thing I have done differently is I used 2 gallons of purified water for my water change.  I usually use tap water but that comes out at 1ppm for Ammonia.  I figured the purified water (my reverse osmosis with minerals added) would be not just good, but a great idea.
 
Any ideas?  The little fish corpses are unremarkable.
 
Thanks

The water change was about 5 days ago

 

[EllieJellyEllie]

Did you match the temp, pH, etc?
 
Also, did you condition it and test it with the test kit?
 
Are you using test strips or drops?
Oh, five days ago. NEvermind. I dont know Sorry

 

[jdubs]

The tests were done with API test kit (drops). 

 

[dave840f1]

It could still be the PW at fault even after 5 days. This water and tap water only has to be good for human consumption not keeping fish in so it does have additives to make it safe for us to drink. (Not good for fish).

 

[Shelster]

It could still be the PW at fault even after 5 days. This water and tap water only has to be good for human consumption not keeping fish in so it does have additives to make it safe for us to drink. (Not good for fish).

I think op meant he used reverse osmosis water.

What was the brand name of the minerals you added, and how much did you add?

If anything, you would think the shrimp would suffer ill effect first?

 

[Maehlice]

I figured the purified water (my reverse osmosis with minerals added) would be not just good, but a great idea.

 
How did you measure and match the GH of the RO+minerals to your tap water?  Rapid changes in GH and conductivity can also cause mysterious deaths like this.
 
Also, is your tank planted, or did anything change in relation to the lighting or planting?  Maybe it was a rapid overnight pH shift.
 
The only other thing that comes to mind is a water or air pump that was accidentally turned off with the lights -- in which case they could have suffocated.

 

[jdubs]

I used Nestle Pure Life water that uses Reverse Osmosis.  It is a planted tank with Fluval Shrimp substrate (to help promote a stable PH).  Shrimp are still fine as of now.  There are even some very young shrimp that seem to be doing fine.
 
I did not match the RO minerals to my tap   It was bothering me that the ammonia in my tap water is so high, so I thought I was doing a good thing by using purified water.  I have used distilled once or twice in the past, but I heard that that can be bad because it is void of minerals and can throw off the PH.
 
The water change was about 20%.  Everything else seems normal and with no other unusual events to report within the last 5 days or so.
 
I am very perplexed about this. 

 

[dave840f1]

Sorry I did not read it correctly. I use RO water (my own unit) and have never had a problem and I never add additives. I use this about every 3rd or 4th water change. The only additives I add are macro and micro elements in plant food added daily.

 

[SarahR]

I'm not sure what happened, but just out of curiosity I would buy another bottle of the Nestle water you used and test as many parameters as you can.  It may tell you nothing.  When they add minerals to bottled RO water it is strictly for taste.  There is probably no real rhyme or reason other than to make it taste better, so heaven knows what is added and at what levels.  

 

[jdubs]

I will do that.   I actually have one more thing to add.  My husband told me the light got left on all night 2-3 days before they all died.  It is on a timer, but I must have turned it on one morning to check it and forgot.  Could it have stressed the fish too much?  I know that it is not healthy to have that happen, but I wouldn't think they would die....hmmmm....it's a mystery

 

[SarahR]

I can't see how one extended period of light would have caused even very much stress let alone a mass die off. Hopefully you will figure out what happened, but you may never know. Nothing occured that would have resulted in substantially lower oxygen levels the night they all died, did it? Temporary power outage while you were asleep?
Another left field idea is to check that the heater is functioning properly- heaters can malfunction in a number of ways including overheating, not heating, or leak current into the water. All the fish and none of the shrimp means something shrimp can tolerate.