Backyard Aquaponics
A place to discuss aquaponics

Forum member Popeye came into work yesterday, he is a farmer and like most farmers around here has yabbies in dams, I dropped Popeye off some trout out of the same batch I lost all of mine, his are going great, I explained that dead yabbies caused my problems, Popeye said that yabbies like to shed shells in shallow or no water! and generally die if in deeper water!
This makes sense as some of the ones that died and floated were halfway through shedding, I couldn't work out why, water tests were as they had always been, he suggests having things in tank that yabbies can climb up, also members that keep yabbies in shallow tamks would not experience the problems I and others have had,
I am still over yabbies and will get them from farmers when I need them, a luxury a few wouldn't have but as mentioned I still think you need bottom feeders to clean things up, so still going with the cobbler, blue marron in tank 2 are going great, I am surprised they didn't die when I was having the trout problems

Yeah... I did read from some webpage that when yabbies are going to moult, they go towards shallower waters to do so... I did noticed this behaviour once or twice, when I drained my yabbie tank to quite low and refilled it...

from my experience with yabbies, if they are half way through shedding and dont make it, they might be lacking calcium in the system. Adding egg shell, uncooked prawn shells or calcium carbonate to the water helps.

Yes Kroz I have shell grit in the system at all times, but I will stick with Popeyes theory as he has observed their behavior in dams, yabbies eat their shedded shell for a calcium boost, I still think the risk compared to return isn't worth it, a couple of dead yabbies easily poisoned 6000lts of water, return for me out of 200 or so after them killing each other and the deaths from shedding was about 6 plus the loss of 40 trout and about 50 mussels, so again to me not worth the risk when there are thousands within a short drive, to use them for cleaning the system was a complete backfire and the bottom feeding fish will be a much better choice, if they die then they float

Gee Nocky, don't like hearing of such losses
I'm wondering if I've overlooked the issues using a PVC (pool) liner

I'm thinking trying mussels - as well as treating suspended algae -
they'd die off, if toxins from PVC were present?

I shouldn't have prob's with moults, as PH is around 7.5>
& only 15cm water depth

hay guys, for those of you who have yabbies in your system you can try the shade cloth hides that marron farmers use that sit verticle in the water column, i use them in my system and often see yabbies with in a few cm of the surface when they are ready to moult, they also seem to help them escape canabilism.

cheers.

Just a quicki on yabs

We had one rock up on our back pattio bout march this year, poor lil bugger was dry and sick we put him in a tub with some gravel and airation went awesome fir ages then we let him go wish he was here too see my ap system haha we traded up to a rabbit!!!! Kids love the rabbit as it's a tad more social!

Thats an interesting point you bring up Nocky, reading your post re: yabbies and your problems with them it had nearly put me off yabbies, but I have had no problem with the 2 (pet) ones that I have in my aquarium/prototype setup. I have had them for over 12 months.
how shallow is popeye talking? the depth of my aquarium would be no more than 200 - 300 mm.
and my proposed yabbie tank in the expansion system will fluctuate from 500mm to say 100/200mm. I hope this will be sufficient for them.

BB you shouldn't have problems with 2, Popeye see's them on the banks at times, but many people have them in Grow bed size tanks same depth you're talking, I think Chillidude has had problems with his though in a shallow tank and I think CD is about over them as well, Rick has also written about similar problems, I had around 200 and during the shedding period had many floaters but if they die in a hide then they just stay and go off, and is generally too late when you discover the problem, also a big job pulling out the hides to find it.
Yabbienut the mussels died from being eaten by the Yabbies, mussel will live in radioactive water nearly you have to get the right mussels, to my knowledge there is only one variety that will live in still water IE tanks, they filter 20-40lts of water a day each, I also have 4 in an aquarium inside and only have air and no filter, water is always crystal clear, we did a pH test on a nearby dam it it was over 7 so I would think popeyes would be similar, and they still come out to molt, I'm not suggesting 150mm would cause you problems, and at that shallow depths it is much easier to see if their is any problems.
BB I would still have a mesh hide for them to climb, you can by the on Ebay or make them out of shadecloth, I didn't have a problem in the first year, maybe because I only had 50 or so but when you do have a problem it is irreversible and you just have to wait until it fixes, I am not suggesting not to try yabbies, just highlighting problems that can arise, as I said above, for me Risk compared to return isn't worth it, 6 eaten out of 200..........

Good to know Knocky - I have always envisioned using a BYAP growbed as a yabbie tank. Plenty of bottom space for them, but nice and shallow. The other thing I thought of doing was using strapping tape to tape a whole bunch of PVC pipe together. Then when you take out the hides, you just pick it up by the strapping tape and you get the whole stack.

you can build a block of flats Gemmell, they will climb into them, pyramid 3,2,1 I used glue for mine and worked fine

Seems yabbies need high PH to keep their shells hard
7 is minimum - 7.5>8.5 more suitable, but not so for vegies etc.?
I'm looking forward to setting up aquaponics SOON, but
will keep yabbies in current filtered pond - I see the koi boys are using
cheap PVC pools with no ill reports.
They are happiest in turbid water (suspended clay) & apparently
are not aggressive or cannibalistic in those conditions
The next best thing is green water as long as oxygen levels are kept
up of a night time
Hmm... might just dig a shallow trench with liner, put some clay on the bottom
couple of airlifts & reed beds or raft plants
Hardly seems worth it, but I'm aiming at a thrive - not just survive - situ
& yeah Nocky, same here, can catch or buy them much easier

Well actually ,... they need calcium for their shells to harden after moulting... although they do have a calcium deposit within their bodies, which along with the old shells.. they will often eat... thus reabsorbing the calcium...

Carbonate hard water... is by definition rich in Calcium.... thus is usually higher in pH... or vice versa...



hahahaha... want a bet....

Turbid water... ie in dams ... might help them hide... and/or they may burrow... hence greater survival rates...

Over stock them in any conditions.... and they'll either migrate... or fight to the death...

Oops ... should've said not as aggressive ...
& phytoplankton (green water) which I have found - just now -
better to leave that way, so no need for
mussels, barley straw or phosphate removers.
Even tho' my phosphate levels read 0 - API test kit -
I think it only reads dissolved & not solid phosphates
(or sumtink like that)

I'd like to grow out a couple of marron too, but apart
from same PH needs, other parameters are at the other
end of the scale

Yes, you're right about over crowding Rupert
I told a mate about the stored calcium gastroliths
He thought I was BSing, so we went out & caught some & cooked 'em & ate 'em
& showed him the gastroliths, well worth the outing