Backyard Aquaponics
A place to discuss aquaponics

Its been a very long time since i have made any post's but this Aussie winter has been disastrous for me. I need some advise on what could be killing my fish.
I have recently lost all but 2 of my largest Koi and goldfish in my pump tank (over a few months one at a time) and i have no reason why. Test strips indicate water is optimal with nothing that jump's out as an issue. I have not been feeding at all due to water temp and completely no interest from fish what so ever. I lost a few in my sump tank as well but they seem to be doing OK at this point so its not like there is something in the water. I believe it has something to do with temp and either over or under feeding (only feed once every like 3 weeks on really warm days)Fish are 2 years old and have been over wintered before without feed and zero losses so I am really not sure what could be going on. Any advise would be amazing thanks guys

Hello ,sorry to hear of your problems, one question that I will ask and that is where are you getting your water from? The reason I ask is that if you are using rain water off a galvanized roof it could be a zinc problem. You have the same problem if you have a zincalume roof. I think you call it galvalume. If this is the case you can either paint the roof or get the water from somewhere else. If this is the problem you usually don't loose them all at once but just in ones and twos.

Thank you for the input! I have been using city water tho for all filling and top up with a water conditioner each time. I ended up draining off 500L of water (about 1/3) water volume and refilling and fish seem to be much happier. I intend to do another 1/3 water change but have to get some more water conditioner. I suspect some type of water issue however test strips indicate its fine. Starting to think test strips are to old to do what they are supposed to or there was indeed some type of metals poisoning in the water. The only thing I can think of is that the growbed (400L of IBC cut off and fliped up with original IBC cage) has a galvanised cage and is positioned over top of the sump. Any time it rains would leach a bit more zinc into the water. Other than that.. I am at a complete loss. Over all i have lost probs close to 10 20 - 30cm fish over the winter and very much regret not doing a simple water change earlier or at the fist lost or signs of distress. Still have 6 big fish so i guess ill jsut start over with another 12 or so fingerlings and grow them out again.

What a shame to lose such nice sized fish! If you have another one get sick or die, perhaps you could submit it to a veterinary diagnostic laboratory for necropsy. They can’t always determine the cause, but it might help you prevent losses in the future. Have you tried using the water quality test kits rather than strips? I’ve read that they’re more accurate, although I’ve never done a comparison. I hope the water changes have solved the problem.