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PostPosted: Sep 20th, '18, 10:02 
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Hi all,

I'm having problems lately with my tilapia as they have been dying. A couple die each day since i put them in the system. I'm trying to pinpoint the problem currently.

System Details:

1 IBC fish tank and 3 halves of an IBC for Grow Beds with Pumice as media. Total of around 2000 Liters in the system. The system has been running for almost 2 months now.

I poured in 2 liters of an off brand liquid seaweed extract to start the cycling process and immediately started planting vegetables. From my tests I found out that the liquid seaweed was causing the high pH of 8.0 - 8.2.


I tested my top up water and it was only at around 7.2. I also kept a bottle of water with some media inside and the pH of that was also around 7.2-7.4. I tried testing an isolated batch of top up water with the off brand liquid seaweed and the pH test came out at 8.2-8.4.

My regular test readings are:
pH - 8.0
Ammonia - 0 ppm
Nitrites - 0 ppm
Nitrates - 10-20ppm

I already tried adding a bit of distilled vinegar into the system to try and lower the pH, although i have been adding it in small doses. I haven't really seen any progress though. Another option I was considering is a partial water change to get the liquid seaweed out of the system.

Additional tips from you guys would be appreciated.

Thanks


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PostPosted: Sep 20th, '18, 15:02 
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Sorry to hear about the fish troubles. Sounds like it could be because of an earlier spike in either ammonia or nitrite. This could have happened during transport to your system or during cycling. If the spike is too high then the fish suffer damage which causes a gradual die off. The high pH probably didn't help since ammonia toxicity is greater at higher pH's (and higher temps as well). In new systems it's usually a good idea to salt the system water with Sodium Chloride to 1 part per thousand because the chloride ion competes with the nitrite ion and gives some protection against damage due to nitrites. I would increase the aeration and salt the water if you haven't already but you'll probably still lose some fish because my guess is the damage is already done - hope I'm wrong though.

That's my best guess :dontknow:

Guess I should also ask what the ingredients of this seaweed extract are - some of them contain ammonia or another nitrogen source that might cause problems in a system with fish already in it.


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PostPosted: Sep 27th, '18, 15:18 
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Hi, I appreciate the reply.

I'll try and salt the water maybe it will help. I also have solids building up in the bottom of my fish tank. I don't know if that might be a problem?

Anyway I added a new batch of tilapia fry two days ago, I got zero deaths after one day but I had 10 deaths so far after two days. The dead fish all had red/purple gills I'm wondering if that's ammonia poisoning? I'll try siphoning out the solids at the bottom of the Fish tank maybe they are causing ammonia spikes.

Readings are still the same

pH - 8.0
Ammonia - 0
Nitrite - 0
Nitrate - 20

Thanks for the input


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PostPosted: Sep 28th, '18, 01:32 
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A couple of thoughts. When you get new fish make certain you acclimate them to the system water. A lot of times the difference in the water is enough to kill fish from shock.

I think removing the solids is a good idea. You do get a biofilm coating on the tank and this is normal and should be left alone. If you are getting something other than this where the solids are building up, these patches can go anaerobic and generate gasses that are toxic to the fish so it's best to be rid of them. Only feed the amount the fish can eat during the feeding period and remove anything that's uneaten.

Sounds like it could be ammonia poisoning. I'm not absolutely sure about the gill color with ammonia poisoning, I know with nitrite poisoning they are more of a brownish color so it's probably not that. If the gill color looked off to you then it wouldn't surprise me if it's ammonia poisoning in this is the case.

Did the fish look like they were having troubles getting oxygen or were they up near the top or in the air (if your aerating separately) or water streams? A lot of times you'll see this if they have gill damage.


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PostPosted: Sep 28th, '18, 15:53 
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I put the bag, where the fish came in, in the fish tank for 30 minutes before pouring them in. They managed to survive for a day without any problems then they started dying off quickly.

I had another round of fish deaths today, 20 in total. I added another air stone to the tank and it helped in clearing up the solids accumulated in the bottom.

Ammonia readings came in at 0ppm so I'm wondering if it really is ammonia poisoning? Some of the fish gills look like they're bleeding. I asked a friend who is into aquaculture and he said it might be a bacterial problem. Would salting the water help with the bacterial problem?

Most of the fish stay in the bottom of the tank and only come up when I open up the fish tank to feed them. Then after eating they settle to the bottom again.

I am baffled as to why my fish are dying.

Thank you for responding


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PostPosted: Sep 29th, '18, 07:54 
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It's pretty unusual to lose that many all on the same day with a disease but it is possible. I doubt that salting will help if it's caused by a bacteria (at least at the normal treatment levels). On the other hand salting does help with stress and helps the fish build a slime coat. If this is a water borne infectious agent then adding a UV sterilizer to cut down on the number of infecting organisms might help as well.

I'm not really convinced that this is an infection, mostly because of the timing - Usually something like this is because of some physical/environmental problem.

Stop feeding if you haven't already (if they are really small you may have to feed but larger fish can handle long periods without feeding).

Increase the aeration.

Stop messing with the pH for now, it will come down on it's own eventually and I'd like to remove this as a possible cause of issues. Adjusting the system water directly and having wide pH swings is hard on the fish and might have something to do with the deaths. Tilapia are tough but not indestructible.

Make sure you're doing the tests correctly and that they are actually working right (anyone have a kit you can cross check with?).

How many fish are there in the system now and how big are they? Post up some pics of the fish and the system.


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