Yabbies are pretty easy to keep/breed n raise,there will be a massive loss in babbies as cannabalism is huge,out of 500 babies only round 10% will make it to adult hood.I have found the best way to stock larger densities is to design the tank as a multilayer set up,using things like milk crates n pvc pipes of various sizes,aswell pull out all the egg carrying mothers & as soon as she drops the bubs put her back to the main tank.The babies are able to look after themselves straight after releasing from mother,the babies will eat a hell of alot of different foods,foods ive used are potato,carrot,fish pellets(sinkable type) & one of there favs is lucerne(i used to soak 1st),as in any food you feed you must keep an eye on how much it pollutes water.