Backyard Aquaponics
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Have lost about 40 Barramundi in the last 7 days, the infected fish all have a pale discolouration to the last half of their body. The fish did go through an ammonia and ph spike about 2 days before the deaths began. Any advice would be very much appreciated.
Current ammonia 0.25, nil nitrite, nitrate 5, do 8mgl, ph 6.8, salinity 980ppm, temp 24 degrees c.

Sorry to hear about the fish.

Are you seeing any behavior issues like swimming near the top and gasping for air?

Knowing that they've been through an ammonia spike I'd probably aerate as much as possible since they may have damaged gills. Salting the water might help or putting them through a salt dip. Salting the system water to 1 part per thousand with NaCl (Sodium Chloride) is good for stress and helps the fish build a slime coat (1 ppt will do in any strawberry plants in your system but the other plants should be fine). The other thing about this is the chloride ion will help protect them against nitrite toxicity - wouldn't surprise me if nitrites spiked after the ammonia - it may be too late for this to do any good but it can't hurt.

If you're sure this is a disease then a salt dip at a higher concentration might help. I'm not sure what gets used for Barramundi but someone will hopefully chime in.

It's common to get fish deaths for quite awhile after a spike usually one or two at a time (after the initial kill).

Hi scotty 435 thanks for the Reply

No Swimming at the surface and gasping for air, my oxygen levels are close to 100% saturation (have very good aeration). I moved three quarters of the Barra from my quarantine tank to my main system when I had the ammonia spike (I dont think my Quarantine Biofilter was up to the task).

I then salted my quarantine tank to 3000ppm and my main system to 1000ppm and did a 30% water change to quarantine tank(spike was less than 8 hours).

I have never seen any Nitrite in either the Quarantine nor my Main System (both were seeded with Nitrospira 2 weeks before putting Barra in).

Have not had any dead fish in my Quarantine Tank for 2 days but in my main tank I have had 15 deaths all with the symptoms as pictured above.

I am perhaps thinking it is attacks from other fish?. Trying to eat them and getting stuck in their mouths and then spitting them out, Barra are only 40-50mm long.

What have your overnight temperatures been? Even at 24C your are down at the low end of their tolerance range.

The optimum temperature for Barramundi culture is 28°C, with acceptable growth rates between 26-30°C. Temperatures below this range will result in decreased metabolism and growth.

The ammonia spike won't have helped, and low overnight temps will only add to the problems.

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My System:
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My Fish:
https://www.youtube.com/channel/UCtiiZv ... iWEVFANEVQ

Fish can die for a few days after a bad spike, even if you return the levels to normal. Also you can have fish die for weeks afterwards from other infections because they become more susceptible.

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Hi JoBlow

My lowest overnight temperature is 24 degrees (heats up to about 25 during the day), the fish are in a indoor insulated room which is temperature controlled. I might dial up the heating a degree or two, I only heat during the day when my solar generation offsets the use of a heater and the thermal mass of 7000 litres indoors only drops overnight by 0.3 to 0.5 degrees.

Cheers