Backyard Aquaponics
A place to discuss aquaponics

I have been having a problem with my murry cod dying I have been losing about 1 a week. For the last month, they are about 4 inch long and appear unmarked.

I had thirty in a 500L sump, the only thing I notice is they all die with the mouth and gills wide open. Oxygen is adequate to keep the trout healthy so that is not the problem.

Water tests
pH 7.4, ammonia 0, nitrite 0, nitrate 40

Main tank has 2 15" trout and 30 5" trout they are all fine.

Water temp is 10c may have been as low as 7c

any ideas on what may be wrong?

As they're a Murray fish, I'd look at what their temperature tolerance is. I don't know, just a suggestion... they may not like exposed tanks in Melbourne during these months.

Cold is an issue with Murray cod, and if heavily stocked have a tendency to die for no reason,that's just cod!

Are they eating.

unlikely Duff, considering they are dead

I would suggest temp fluctuations have got them.

I walked straight into that.

But are any of the live ones feeding. I know cod and golden perch like live food and some will live on pellets but most tend to go the other way. George is still with me cos he hunts insects and I give him chunks of fish and live food when ever I can. Not even sure if he ever eats the pellets I throw into his tank.

They seem to be eating ok, but I lost another over night

i am having the same problem here in bendigo loose about 1 a week, wouldnt do cod again. the silvers are still feeding,water temp 8 deg

Might be too cold for cod that small. Even silvers go belly up over winter if they are not big enough.

How long ago did you get the cod? Are the *live* ones feeding ok? Do you actually see them feeding? Do they look nice and fat or a bit thin?

From the top, those that feed seem to be fat right up until the tail. The ones not feeding seem to look thin from just after the head back.

I have some m. cod (about 2-3 inches long - in Adelaide) - randomly mine tend to die too. I had a lot die at the start due to problems with not taking to pellets. But they love peas for some reason and tend to feed better with a light on at night than feeding during the day when they just want to hide from people peering in.

It's the first time I have had cod so I am guessing they are feeding due to the fact they are much heavier than when I got them and there seems to be no obvious food floating around. I do think I was under feeding for a while but it is only since the cold weather that I have had the current problem.

Some of my reading indicates that they have problems with the cold.

My original idea was to move them to a warm water system in the green house but it had not happened due to other projects and a back injury. I am hoping to get that system setup by the end of the weekend.

I thought the minimum temp for cod was around 14 degrees???

9 -34.... optimal 20 - 25.... according to the literature... but one or two have even been caught in the cold waters of Lake Eucumbene

Just an update for any that may find this problem in the future.

I moved the Murry cod into the new greenhouse setup I am also heating the tank to maintain above 13 degrees, I have not lost any fish since

Hmmmmm might have to keep an eye on my water temps. Seem to be doing alright at the moment. My Water temp 13deg.