Backyard Aquaponics
A place to discuss aquaponics

Having had lots of salads, a few tomatoes and the occasional smoked jade or silver perch over the last couple of years, I'm up for something a bit more challenging. Have been working on the idea of barra or trout... but my climate here in northern NSW is too cold for the former and too hot for the latter - without taking out a bank loan to pay the power bills.

I've settled on Murray cod and it's too late to change my mind. 20 x 10-12 cm fingerlings arrive later this week.

They're apparently weaned on to pellets already. They'll start out relatively crowded in about 200 L of water... on the understanding that crowding reduces territoriality. I've also salted my water to 2 ppt and have air stones and good water turnover.

I may well have bitten off more than I can chew. I find lots of posts about people starting out with MC... but the threads tend to peter out... can't find anyone claiming to have raised them to eating size

Any advice welcome.

I did, but they were mostly very slow growing and I lost a lot along the way. They were much smaller than yours to start with, and supposedly pellet trained, but would never eat pellets the whole time I had them. They would eat blood worms or ox heart, but that was expensive, and they didn't taste as good as trout, so I won't grow them again. I still have one left in my small system, this year's trout are already as big or bigger than it, and it has been in there since the start of 2014!
You can read about my experiences with them from Jan 2014 in my small system thread, including pics and videos

Thanks Gunagulla... have just skimmed through the relevant section of your thread. Have previously read some of your posts about the troubles you had feeding them with pellets and unexplained deaths... also the deaths explained by biggest ones eating their mates.

But I hadn't previously seen the bit about their performance on your BBQ. Your thread was very helpful... and just a little bit encouraging.

It seems that various forum members have found that MC that were supposedly weaned on to pellets went off them as soon as they left the suppliers. I've got my fingers crossed that my slightly larger fingerlings have been on the pellets long enough that this doesn't happen. I'll find out on the weekend!

Quick update for anyone interested in Murray cod.

20 x 10 cm fingerlings have been in my smaller system about 5 days now
system under a deck and artificial lighting - with good growth of lettuce, basil and some marigolds
250 L growbed with clay balls - not enough to grow out my MC but plan is to move them to bigger system in summer.
currently 200 L of water in FT and about 350 L in total
All water being turned over at least every 30 mins... probably quicker than that
Running constant flood at present... so I can keep my FT volume low
have a radial flow filter set up
two airstones and water returning to FT in 3 places... so heaps of aeration
Water looking crystal clear... apparently MC are sensitive to water quality
Ammonia etc under control.

The fingerlings ate nothing for the first 4 days... I only offered them 3 mm floating native fish pellets as was told they were weaned on to these. Was tempted to offer worms or ox-heart. But worried that, once eating something other than pellets, they might never go back.

Two days ago I put a heater in the tank (system is very well insulated)... having read that MC are reluctant to eat pellets at temps under 20 C. My water has been between 15 and 16 recently.

Yesterday they ate the majority of the roughly 30 pellets they were offered... though they remain very shy... pellets were eaten after system covered up. They just sit motionless on the bottom of the tank - most of them hiding under the pump. So can't post decent photos at this point

I can't be sure the heater made the difference... maybe they just got very hungry. With luck, I'll be able to phase the heater out once they're settled in and eating reliably.

I have a long way to go before I'm eating MC for dinner... but so far so good!

Starting with 10cm fingerlings, rather than the tiny ones I had, should help as they probably really have been eating pellets. I'm not convinced that mine had ever seen a pellet before I got them.
Sitting motionless is what they tend to do for much of the time.

Given the temperament/behaviour of Murray cod, and the way they eat everything up to and including golf balls, birds, and each other... they're not sitting motionless. They're lurking.

lurking with intent! (to smash the pellets as soon as my back's turned)!

They seem to have eaten almost all of their breakfast today... will be feeding them a little bit more with each meal over coming days. I've seen youtube videos of them being hand fed... so, with a bit of luck, they'll become less shy in a while.

Nearly a month since the MC went in to the tank.

Still no deaths. Still all 20 manage to hide under the pump. But they come out to feed when I've gone... can spy on them with a security camera I have trained on the tank and they look pretty healthy. Will try to get a decent video of them eating and upload it

Hard to see if they've grown... not much, if at all. Still only eating a couple of 3 mm floating native fish (perch) pellets on average per day. I'm hoping they'll get hungrier when spring comes.

I wonder if these would do better on a sinking chow during your cold spells, that's definitely the case with bluegill during the winter here. Try giving the chow your using a soak for a few minutes and then give them a squeeze to press the air out - then see if the MC go for these more than the floating ones. It's a bit harder to ensure a clean tank but worth a go I think.

Thanks Scotty... will give that a try and report back.

Nearly 6 weeks in to my adventure now...

20 x MC still all alive as far as I can tell. Not sure if they've grown or just getting brave... they don't seem to all be able to fit under the pump any more... their tails are hanging out and one occasionally has a little swim around.

Have upped their feed a bit... maybe half a tablesoon a day now. I assume they're all eating at least a little. I know they can go for a while without food but 6 weeks seems a bit long... none of them look skinny when they come out.

Am dying to feed them some live food... but determined to stick with the floating pellets until I'm really confident that can be their main food source.

I tried the sinking pellet trick Scotty... I couldn't tell if it made any difference... none of them rushed out to grab it, but maybe they finished it off later on.

Every fish is different . With the Bluegill the food gets hit on the way down and maybe some gets plucked off the bottom. Once it hits the bottom most of it gets cleaned up by some Channel Catfish but that usually happens at night. Sounds like your Murray cod like to eat on their own .

I'll be watching this closely. What is your water temp with the heater in?

About 20 degrees.

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