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Posted by andy smart on May 9, 2005, 3:46 am
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We are a secondary school, with a tank of coldwater fish in our lobby.
They have always been happy and healthy with no problems, over the
weekend of the 30th april we lost 4 of our goldfish and one of our
loaches - they were just floating on the surface on the tuesday morning.
The remaining fish were looking less lively than normal but were
interested in food. The shoal minnows (no idea of their real names) were
lively and as per normal. Over the course of the week we have since lost
all of our remaining goldfish and our other loach - they've not really
recovered and have been sitting on the bottom of the aquarium unless
it's feeding time when they come up.
We've cleaned the filter twice during the week and there is no obvious
foreign body in the water. The tank is large and has a lot of vegetation
- it's been a couple of months since we last added new fish, these came
from somewhere reputable and were the last to die.
Our first thought was that something had been put in the tank, either
via accident or malice, but I can't work out why these minnows would not
have been affected too. I've been though the websites for common fish
diseases and can't find anything which matches the symtoms. A couple
seem to have either lost their dorsal fins or were keeping them flat
against the body, but not all. Also if it was fin-rot it came on out of
nowhere and was very suddenly fatal.
Any ideas would be very welcome.
andy
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Posted by Geezer From The Freezer on May 9, 2005, 10:22 am
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Andy,
How big was the tank in terms of litres or gallons, how many fish?
Did you ever change any of the water?
What were the ammonia, nitrite and nitrate levels. PH levels too?
How did you clean the filters?
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Posted by andy smart on May 9, 2005, 10:56 am
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Geezer From The Freezer wrote:
> Andy,
>
> How big was the tank in terms of litres or gallons, how many fish?
> Did you ever change any of the water?
> What were the ammonia, nitrite and nitrate levels. PH levels too?
>
> How did you clean the filters?
Thanks for answering!
No idea what the literage is, but the dimensions are 120x40x35. It would
have contained ~ 8 'goldfish' of varying sizes and ages, 2 loaches, and
4 of these minnows. It's been up and running in it's present form since
around september, we moved it from another part of the school.
We replace evaporation using distilled water we make on site as required.
Don't know about nitrite and nitrate, but PH is 7 today.
We clean the filters by taking it apart and flushing it under hot water
till it is clean. It's one with two chambers of mesh with a central core
of filter wool (if that makes any sense) - it was last cleaned fully
around six weeks ago and was not particularly clogged after the sudden
death of fish over the weekend.
I had a good look at the fish which expired today, and apart from being
slightly ragged round the dorsal fin they do not have any visible
symptoms. What struck me was the suddeness of it, going from no visible
sign of trouble on friday to large numbers of dead by tuesday.
best wishes
andy
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Posted by secret squiddle on May 9, 2005, 12:51 pm
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"We clean the filters by taking it apart and flushing it under hot water
> till it is clean."
You should never 'clean' a filter with hot water. What I suspect you have
inadvertently done is killed all the friendly microbes the were living in
the filter, so the filter was sterile.
Filters work in two ways.
1. They mechanically remove solid dirt particles (or at least trap them)
2. They are home to thousands of micro organisms that eat the pollution from
the fish and render the fish waste harmless. Hence these bacteria are good
bacteria - and should be cared for accordingly.
In future only rinse the filter in tepid water (icy cold water can kill them
also, but not as much as hot water - which will eradicate 99% of the
microbes). Rinse in clean aquarium water is best to maintain the harmony of
the filter.
So without those friendly bacteria 'eating' the fish waste, the water would
have quickly become polluted - resulting in the death of all the fish.
For the same reason when restocking the tank (clean the tank and remove all
the water - you can use hot water to clean a fresh tank - just incase
there's anything bad from the stressed and dying fish, living in the water)
only introduce 1 or maybe 2 small fish to begin with. Only do this after the
tank has been up and running for at least 2 weeks (with the filter running).
The filter will take time to start working to maximum efficiency.
Also it's worth pointing out - that the filter should be running 24hrs a
day - to maintain the good bacteria in the filter. When you switch it off -
the bacteria can't feed and die.
**SS**
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Posted by andy smart on May 10, 2005, 4:03 am
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secret squiddle wrote:
> "We clean the filters by taking it apart and flushing it under hot water
>
>>till it is clean."
>
>
> You should never 'clean' a filter with hot water. What I suspect you have
> inadvertently done is killed all the friendly microbes the were living in
> the filter, so the filter was sterile.
>
> Filters work in two ways.
>
> 1. They mechanically remove solid dirt particles (or at least trap them)
> 2. They are home to thousands of micro organisms that eat the pollution from
> the fish and render the fish waste harmless. Hence these bacteria are good
> bacteria - and should be cared for accordingly.
>
> In future only rinse the filter in tepid water (icy cold water can kill them
> also, but not as much as hot water - which will eradicate 99% of the
> microbes). Rinse in clean aquarium water is best to maintain the harmony of
> the filter.
>
> So without those friendly bacteria 'eating' the fish waste, the water would
> have quickly become polluted - resulting in the death of all the fish.
>
> For the same reason when restocking the tank (clean the tank and remove all
> the water - you can use hot water to clean a fresh tank - just incase
> there's anything bad from the stressed and dying fish, living in the water)
> only introduce 1 or maybe 2 small fish to begin with. Only do this after the
> tank has been up and running for at least 2 weeks (with the filter running).
> The filter will take time to start working to maximum efficiency.
>
> Also it's worth pointing out - that the filter should be running 24hrs a
> day - to maintain the good bacteria in the filter. When you switch it off -
> the bacteria can't feed and die.
>
> **SS**
>
>
Thanks for your input on this SS - we do run the filter 24/7 so we're
doing that right. I'm not sure where the beneificial bacteria would live
in our filter (the filter is very coarse hard plastic with a large mesh
size so there is nowhere for bacteria to thrive except in the core of
white filter 'wool') but I'll use tepid next time. Also remember that
the majority of fish died long before I cleaned the filter with hot
water, but before it was seriously clogged; any ideas as to what might
have caused this sudden initial death?
Could you offer some suggestions as to why one species of fish all
survived with no ill effects, while two others all died? If some species
are more 'tender' then perhaps we should avoid these?
Thanks again
andy
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>
> How big was the tank in terms of litres or gallons, how many fish?
> Did you ever change any of the water?
> What were the ammonia, nitrite and nitrate levels. PH levels too?
>
> How did you clean the filters?