I'm a beginner with aquaponics. I built my first IBC system in the early spring, cycled it, and stocked it with 25 2.5-3" koi about 2 weeks ago (5/16 to be exact).

When I received the koi, one of the 25 had already died in transit.

Water chemistry when I stocked was...

Ph = 7.4
Ammonia = 0ppm
Nitrite = 0ppm
Nitrate = 40ppm

After stocking, I got a little Nitrite spike... up to about 1ppm, but then it settled back down after a few days. My seedlings are growing and my fish are dying so now my water looks like this.

Ph = 7.4
Ammonia = 0
Nitrite = less than 0.25ppm
Nitrate = 10ppm

Water has remained clear the whole time.

After stocking I lost 3 more fish the next day. I figured it was transit related shock and that it would pass with time. But here I am am 2 weeks out and my koi are steadily dying a rate of about 1 per day.

They are also very skittish. They are not coming up to the surface to feed like I'm told they should. They prefer to hang out in the farthest most hidden corner of the tank all sitting together on the bottom. I have seen some eat occasionally when a food pellet passes close by, but they won't come out to eat.

I was concerned that my bell-siphon flush was too powerful and that was keeping them in a constant state of stress, so I have done a number of things to make that flow quite gentle, so I no longer think that is should be contributing to stress. I also added a big plastic tube to give them more places to hide. I figure it they want to hide, let them. But this has not made them any less skittish.

For the last few days I have been coming down in the morning to find an obviously sick fish. I have then scooped them up and transferred them to a make-shift hospital tank. First I tried a 6ppt salt solution, but that killed my fish within 12 hours. Next I tried a 3ppt salt solution on the next sick koi, but that has also led to death within 12 hours.

I now have another sick fish. Here are some pictures.




I'm not sure what else to do. Any suggestions would be greatly appreciated.

Clearly I'm going to need to restock with another batch of fish, but before I do, I really want to figure out how to keep the fish I have alive!

Thanks,

Bill