dmaccy dmaccy
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  • Posted on: 21/7 10:38
Mysterious deaths - all water parameters ok #1
Hi,

I am getting very high mortality rates when we are putting new fish in our tank.

We recently bought shoals of black emperor tetras and purple emperor tetras which were added to a tank which already had partial shoals of each (after a white spot outbreak). The white spot was treated and the tank left for a few weeks, so all clear.

We added 5 new purple emperor tetras and 5 new black emperor tetras recently and have had a large number of deaths . This also happened the previous time we added a shoal of fish and we are at a loss. The only hypothesis we have is that one of the fish in the tank now (it was one of the new ones) appears to have had his tail fin badly nipped and wondered if it were possible for one of the other fish to be bullying the others and causing them to die? But given they are going from seemingly healthy on an evening to being dead the following morning I'm not sure if this possible?

All the deaths are occurring overnight with fish that are seemingly healthy the evening before and then are gone when we turn the light on the following morning.

All tank parameters ok and consistent. Temperature is 24.5 degrees.

Any advice appreciated
Fishlady Fishlady
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  • Posted on: 21/7 11:02
Re: Mysterious deaths - all water parameters ok #2
The most likely cause is a spike in ammonia when the new fish were added. What test kit do you use and is it strips or liquid? What were your results for ammonia, nitrite and nitrate immediately after the deaths (and before any water change)? What are the gH and pH of the tank? How did you acclimatise the new fish?
dmaccy dmaccy
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  • Posted on: 21/7 11:59
Re: Mysterious deaths - all water parameters ok #3
Testing done by Tetra 6 in 1 test strips.

Nitrate and nitrite low numbers (negligible) -little or no colour change on test strip.

Total harness about 10 and carbonate hardness about 10 too.

No ammonia measuring on test strips (used both Tetra and API)

pH approx. 7.2 - 7.5


Acclimatised fish - Approx 1 hour in bag to align temperature, then pour tank water into bag, left fish inbag for 15 minutes approx. Then do 6 in 1 test on water in bag to ensure close alignment of pH.
Fishlady Fishlady
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  • Posted on: 21/7 13:32
Re: Mysterious deaths - all water parameters ok #4
Hi

I'm betting on ammonia as adding extra fish increases the bioload and it takes a couple of weeks for the filter bacteria to catch up. As you haven't a test for ammonia we can't be sure but it's the most likely especially as you also saw some nitrite - even negligible nitrite is a problem for fish and it needs to be at 0. You need to get an ammonia test, and I recommend dropping the test strips in favour of a liquid-based Master Test kit such as the one made by API and the results from strips are not very accurate.
dmaccy dmaccy
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Re: Mysterious deaths - all water parameters ok #5
There is no ammonia showing on test strips. I have used the tetra strips and api and neither show the presence of any ammonia either before or after placing fish in the tank . So I find it unlikely to be ammonia. We also added some tetra safe start to artificially increase the bacteria presence when we added new fish too
fcmf fcmf
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  • Posted on: 21/7 16:56
Re: Mysterious deaths - all water parameters ok #6
Will need to be brief - apologies. Essentially:
* agree that likely to be ammonia for the very reasons Fishlady gives;
* agree also with nitrite - even negligible presence toxic and poses problems;
* test strips for ammonia and nitrite difficult to read and gaps between each level very large (eg ammonia on API 0, 0.5, etc; nitrite on Tetra 0, 1, etc) and thus can hide problems that a more sensitive and liquid-based test kit with smaller gaps between levels would reveal;
* bacteria-in-a-bottle in conjunction with fish-in cycle has very mixed evidence of effectiveness, although Tetra Safestart is one of the more reliable ones - but depends very much on what happens between manufacture and use (during journey, etc);
* especially while you're encountering a problem and during the next month or two while tank cycles during/following last addition of fish, all the more important to have a liquid-based test kit to monitor daily and address accordingly https://www.fishkeeping.co.uk/articles ... ammonia-nitrite-spike.htm

HTH.
dmaccy dmaccy
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  • Posted on: 21/7 19:21
Re: Mysterious deaths - all water parameters ok #7
Thanks for the into both, will get a liquid test and see what happens