Backyard Aquaponics
A place to discuss aquaponics

My foray into growing Murray Cod isn't going too well. I've been steadily losing them for reasons unknown, but finally found some on the bottom of the FT yesterday with obvious symptoms. Now I just need to find out what the problem(s) might be.
I haven't been able to ascertain any info about what it might be from my supplier, he tells me he sees a few deaths each day in his tanks too.
Here is a pic of the 3 dead Cod I found yesterday afternoon, the middle one was a floater and you can see it is decomposing a bit, the other 2 were on the bottom, one still just alive. At the rate they are going, I'll be looking at putting some trout back in by March!
One of the recently deceased is missing its outer skin/scales on its rear, and the other has a red area underneath, which is possibly also present in the decomposing one. I haven't been able to figure it out with online searches.

The one missing the scales on the back half of his body has been eaten (attempted) by one of his mates... this is very common with Murray's, their eyes are waaaay bigger than their belly.

When I had Murray's I found a number of the smaller ones, that had been completely healthy the day before, dead on the bottom of the tank with all the scales missing from halfway along their bodies.

I would also salt the system, possibly to 3ppt at this point for immediate health reasons. Murray's like a bit of salt in their water and I would try and maintain it at 1-2ppt.

Also, what are your water parameters?... Amm, N02, pH and Temp.

...and do you have hides in the tank?... Murray's are less cannibalistic if they are stocked densely (please don't read as heavily) and not provided with hides.

They also have quite shallow bellies, looks like they aren't taken to your feed yet.
You may want to add some brine shrimp to the tank too

I should have added a bit more info- not everyone will have seen my recent post in my system thread.

I'm currently salted to 1.5ppt, and the fish have had some time at much higher concentrations for an hour or 2.
pH has been very stable due to the shell grit and low feed rates, around pH 6.8.
Amm zero
NO2 zero
NO3 60ppm
Water temperature mostly in the low 20s, with up to 26C on a few of the warmer days- ideal for Murray Cod.
I started with 150 in the FT, holding ~4000litres, but I reckon there are under 120 left now, although I haven't added the deaths up yet ( I have recorded all that I have found). I've found 7 in the past 24 hours, although there were a few death free days recently.

As far as hiding places go- I have a ~500mm horizontal 50mm pipe on the SLO with 10mm holes, which is loosely wrapped with fruit fly netting to stop the fish being sucked through to the ST, and another parallel SLO with vertical pipe only, but again a loose wrap of fruit fly netting. They mostly hide under these, and one ~20cm flat rock that is in there, well away from the SLOs, which some also hide under.
I can easily net out the rock and remove the horizontal pipe, but will have to modify the bottom of the verticals a bit so fish dont get sucked up against the netting over the ends if I make the netting a tighter fit to reduce hiding space.

They were supposed to be pellet trained, but I suspect not all are eating them. They are certainly growing, and have increased in length, so I guess at least some are eating pellets, as not many end up in the ST or GBs. I think they eat the biofilm a bit too, as I have seen lots of little tracks in it, but the cover has been advancing and retreating a lot in recent weeks- not sure what is going on there.

Empty tummies. Looks like they are starving these fellas. All in my uneducated opinion of course

Yea, that had crossed my mind. My supplier suggested I stop feeding them, but I haven't. I still have not seen a single pellet being eaten by any of them, but it is a bit hard to see what is going on at the bottom. They are supposed to be pellet trained, but I have serious doubts about that.

The smaller ones will starve if there are hides. I've had Murrays in a large aquarium so have been able to clearly witness their activities. The smaller won't come out to eat, if they do the bigger ones bash them. The bigger ones know where they're hiding and constantly hover over the top. I had a number of pipes in the aquarium as hides and the only way the small ones would feed was if the pellets were to drop within an inch or two of the opening.

None of my Murrays actually died from starving, I sorted it before it got to that, but I've had nervous Barra that did starve to death, it takes 6-7 weeks of not eating, but after about 3-4 weeks they start becoming susceptible to disease/fungus etc.

When I was speaking to the guy from Ausyfish about the Murray's, he was saying they'd need to be weaned back onto pellets after travel. They seem to forget how to eat the pellets.

I've been giving them the pellets at the same time as some bloodworms, and slowly adding more pellets/less blood worms. They seem to be happily munching away on the pellets now. Next job will be training them to come to the surface to feed.

Mine seem to have found hides in the plastic liner, where it ripples. I'm hoping once they get bigger they won't be able to hide anymore. Well so goes the theory.

Good news- this afternoon for the first time, I have seen the Murray Cod actually eat food! Blood worms did the trick, so I'll be feeding them to the Cod for a while to help them put on some weight.
I've taken out the rock and the vertical pipe from one of my parallel SLOs, it is now just a backup overflow. One 50mm vertical pipe remains, with some fruit fly netting zip tied on to stop fish being SLO's into the ST. About 30 of them still try to hide under it, but most are now out in the open.

The good news is that they really go for the Blood Worms, the bad news is that Blood worms cost $45/kg... the Murray Cod would become rather expensive fish if they eat these worms for too long.
The woman at the shop reckons a less expensive way to feed them is with beef hearts + green prawns, run through a blender. Does anyone with Murray Cod growing experience have any thoughts on that?

I guess I could start including some pellets in the mix after a while, but initially I want them to eat a lot of something they like, to make up for lost time, and to hopefully catch up in size to the one monster in there, who must have been eating the pellets and other fish.

I got one of those frozen packed of blood worm cubes, you'll only need one, maybe two of those. So it won't be too expensive.

Just feed them both at the same time, weaning off the blood worms. Mine are happily eating the pellets now.

The packets I can get are only 100g blocks, I think they could easily eat one of them in 2 days.

It's the 100g packets I've been getting too.

I've got 50 of them in my tank (about 4cm long), and give them one cube each morning, with the pellets. I'm currently on my second packet.

If they were already pellet trained, it shouldn't take much to get them back on the pellets.

Mine are very shy little guys though. Although, when they do come out, they are very quick swimmers. They'll zip two meters in a second.

The ~100 remaining Cod here finish off 5 of those squares in a few minutes. I've just given them their 2nd block of 5 squares for the day and they were getting into them with enthusiasm too. I'll give them another block of 5 this evening. Yes, mine are very fast too, zipping aacross the bottom of the tank in a second or two.

I don't believe mine were pellet trained, despite assurances that they were, well, except for one that must be 8 or 9cm long and about 5X the volume of most of the rest. A real monster in comparison to the others, but I've only seen it once so far, so it must be hiding on the far side of the tank, camouflaged by the large patch of biofilm there.

A couple of things that bug me about the packs of Blood Worms, they are imported from China, which isn't particularly environmentally sustainable due to the worm miles, or fish food miles involved, and also the rather dodgy standards, or application thereof, for food production in China.

Does anyone know of an Australian producer, or if it is feasible to grow your own? I'm not finding much of use with internet searches.

I did find someone selling freeze dried bloodworms for over $2000/kg!

Are this lot close to you?

http://www.gumtree.com.au/s-ad/lansvale ... 1037578411

No idea where it's from though (home grown, china, etc).