# Overnight devastation...



## DocPoppi (Mar 4, 2011)

Here's the deal, I just coppied and pasted from another post I just made.
Any thoughts?

As far as a gravel/substrate change, that can be done easily. 
Although I have done many times in the past, it seems I've done something wrong this time.... 
Yesterday I spent the day redoing my African rift tank. I removed much of the gravel and added new black sand, I also put in a new canister filter. Everything seemed peachy when I turned out the lights for the night, but when I woke up this morning.... Total devastation, almost all the fish were dead...
All of the fry seem alive, and the Pleco, along with just a few adults.
All the parameters seem fine... My only guess is some unknown toxin in the water. Gonna spend the day flushing the tank.


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## DocPoppi (Mar 4, 2011)

Is it possible that I had a mini cycle?
My second readings show a higher than normal Am.
And there is likely a bloom, cause water is still cloudy.
After putting an airstone in for an hour, the fish that I could not catch no longer go to the surface. 
In all my years this is definitly a head scratcher!

The breeding in this tank was out of control... But sheesh, that's not how I wanted to solve that problem...


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## majerah1 (Oct 29, 2010)

It would be strange for a mini cycle to wipe out all adults and not the fry.I honestly dont know what it could be.

Did you rinse everything with the new filter out well?What are other params or temp or anything else.What physical signs are the fish showing?


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## Lil Gashog (Dec 1, 2010)

Can you give a list of your decor?Their might be something bad in there.


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## braindoc77 (May 30, 2011)

I've had near-misses like this a couple of times after substrate changes; did you happen to check your alkalinity? Some gravels, particularly for African species, can be a significant source of alkalinity, and by cleaning or changing them out you can have a much less stable pH. Just a thought.


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## DocPoppi (Mar 4, 2011)

Decor is not the issue...
Basically this is a tank that has been up for a year or more, and has had multiple pairs of breeding cichlids, the new sand I added was black sand for cichlid tanks.
My best guess is I created a mini cycle, cause parameters were elevated, but it is odd that most all of the adults were wiped out, and no juvies.
Or an unknow toxin found it's way into the mix? 
Or I had pulled the airstone yesterday, and it is also possible that O2 levels dropped (as the survivors were all at the surface) and within an hour of replacing it all fish I couldn't catch seemed to settle down.
I've done 50% WC and replaced the survivors I pulled out, and all seems ok again.
Like I said before.... I've been keeping fish for a long time (about 30 years) and I can't remember anything quite like this happening.


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## braindoc77 (May 30, 2011)

I actually run airstones continuously for about 72 hours after any major change; too many episodes of finding all my fish at the surface a day after a water change or substrate cleaning. In my tanks, it's usually an alkalinity issue, but not sure what it might be in your case. From what you're describing, though, almost certainly something that affected the availability of oxygen.

This is part of why I've become such a big fan of the beaslbob method; just too many variables to account for otherwise,


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