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 Post subject: Fish die after two weeks
PostPosted: Jul 20th, '19, 19:57 
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Hi ,
No idea what’s wrong with my system . I built Hallam Murray Indy 11.5 system in my green house two months ago .All look good but my tilapia - they die after two weeks ( they die and stay at the bottom ).
Water is 22 c , ph- 7.6 , ammonia- 0.25 , nitrite- 0, nitrite 0. My plants grow better in the soil than in AP. Although I added seaweed extract and my water is brown , not clear .
What did I do wrong ?


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PostPosted: Jul 20th, '19, 21:42 
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Ornela wrote:
My plants grow better in the soil than in AP.

How do you know if you haven't got going yet?

Ornela wrote:
ammonia- 0.25 , nitrite- 0, nitrite 0.

Is the last one Nitrate N03?

Has the system cycled yet?

Where did you get the fish from?

Also,Tilapia are tropical fish,22C is too cold for them but probably won't kill them.

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PostPosted: Jul 20th, '19, 21:56 
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Checked water again:
Ph 7.6
Ammonia 0.25
Nitrite no2 - 0
Nitrate No3 - 0
Water temp 23 c

I cycled the system before o added fish . My plants take up so much water from the system so I have to add rain water , sometimes- tap water ( I put tap water in the barrel and keep for a day or two before adding to the system


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PostPosted: Jul 20th, '19, 22:00 
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How to add photo of dead fish to this conversation?


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PostPosted: Jul 20th, '19, 23:39 
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There are a couple of threads on adding pics in this part of the forum - http://www.backyardaquaponics.com/forum/viewforum.php?f=4

Sorry to hear about your fish. Doesn't sound like a disease, more like some physical parameter that's off. It's definitely a bit on the cool side but they can take much lower temps. I'm a bit surprised they didn't die earlier if there was something about the transfer that caused them to go into shock. I think we need some additional information on your system.

1. Tank volume?
2. Number of fish you started with?
3. Any algae growth? Algae in large amounts can cause the pH to fluctuate and can reduce the oxygen levels in the water.
4. Which type of Tilapia?
5. Grow bed volume and/or any other filtration?
6. Have you salted the system to help the fish with stress? This also helps with nitrite poisoning. 1 part per thousand NaCl works but will cause problems for strawberries if you have them.
7. Any changes that you made just before the fish died? Additions, water changes, anything else?
8. Did they all die at once or was it spread out over a week or more?
9. Any power outages?
10. When you say they die and stay at the bottom - were they gasping for air at the top before they died and then just sank or did they stay at the bottom from the beginning? Did you see any odd behavior like flashing before they died?
11. Is there any metal in or near the system where it might contaminate the system water?

You cycled the system so I'm assuming you got some reading of ammonia and nitrite at some time to indicate that the system was progressing toward being cycled. This makes me think you did everything right and the kit is OK but occasionally someone gets a bad test kit or does the test wrong - even though I don't think this is what's going on, it might be a good idea to verify your test kit is working and your procedures are correct.

Hopefully we can get this figured out pretty quick but if it takes a while you can use something like blood and bone or some other source of nutrients and slow release nitrogen to keep your system going. I suppose you could also use an ammonia source as long as you let everything get processed before you reintroduced fish.


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PostPosted: Jul 21st, '19, 00:32 
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Hi ,
It’s 1000 IBC tank , 2 grow beds - total 4m x 0.8 m and same size raft bed . I have swirl filter and mineralisation tank . 20 tilapias in the tank, blue and rainbow , no algae as my tank is covered and has a lid so no light.
No problems with power , they died within two- three days apart , no metal in the system ,
The only thing I did was I added one spoon of calcium powder and potassium bicarbonate in the sump tank a week ago as my plants started to develop yellow leaves


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PostPosted: Jul 21st, '19, 13:43 
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I doubt either of the additions caused the deaths although they could have caused a shift in pH. The less buffering capacity your system has, the greater the shift could have been. Takes a lot to kill fish though. I'm not sure what's in your calcium powder other than the calcium.

Usually in young systems deaths are due to ammonia or nitrite spikes. The fish don't generally die until later and it's usually a few at a time over a couple of weeks. Typically a day or so before they die, they'll gasp for air at the surface or hang out in the inflow stream.


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