A Yabby farm. This design was described on the AFT forums so I've copied it as best I can. It was a family affair, Nina was in charge of Tyre wrangling. We got an given a scrap 4WD tyre from the local tyre shop.

In an unseen, well shaded part of the yard (between a water tank & garden shed) we laid the tyre over some plastic left over from the concreters doing our build next door. Enough to fully cover the ground below the tyre then more to fold up over & make a lid of sorts.

Then the centre of the tyre was filled with river sand. Fiona found this most amusing & was keen to just jump in & play in it.

After a trim of the excess plastic, then a wipe over to remove the dirt, the tyre was filled with water & the centre sand was also dampened. This made it as respectable as a tyre filled with sand & water then covered in plastic could ever get.

The yabbies were from the pet shop up the road. 10 were purchased, 4 littlies went straight to the turtles. Six big ones were kept for the farm experiment.

This one is a male. The last pair of legs before the tail have pointy out bits on the joint closest to the body. The link above words it as "reproductive or genital papillae of the male crayfish are short projections on the bases of the last pair of walking legs".

This is a female, no pointy out bits as mentioned above & a dot at the base of each of the 3rd legs up from the tail. This one is regrowing one of those legs. The link above words it as "oval openings on the bases of the third-last pair of legs".

Here is a diagram for my own future reference because I'll forget soon enough.

After inspection they were released where they quickly trotted off into the water at the sides. Some vegetables & fish pellets where thrown in & the lid was closed.

The kind person who shared the design says it works well. Cost was nothing, up keep should be flushing out the water if it dirties & throwing in vegetables periodically. The theory is that the tyre keeps them warm & insulated, the sand offers them opportunity to hide from one another, the plastic bottom stops them burrowing to freedom, & the cover keeps them relaxed & not worried about being eaten...