This may amuse others...
I had a feeling my 'worm farm' wasn't quite so much farming worms as releasing them to the environment... Poking through the morass the other day I didn't find one worm! Plenty of beetles, larvae, evidence of rat burrows, oh my!
So the worms have fled the coop, so to speak. :-)
Meanwhile every time I open the plastic compost bin lid I find a host of worms hanging around the rim of the lid. It makes me laugh — worms galore where I don't intend to farm them; none at all in my dug-in worm farm. Whenever I pick up something that's been sitting in one spot for a while (e.g. flower pots) I find worms!
The official 'worm farm' is proving all a bit too much effort for too little return, frankly! So I might forget about organised worm farming and go for something else instead.
The new plan is to find a large piece of heavy flexible material like rubber matting, old (unsprayed) carpet or even sheet plastic. This will be laid out in a large area on top of a sprinkling of kitchen waste. After several weeks I would hope to find a nice nest of redworms living under the fabric.
Well, that's the theory... And based on the number of times I've lifted a flat heavy object off the ground and discovered heaps of worms, I can't see why it wouldn't work. The large surface area (as opposed to a limited worm farm) means I maximise the chances of having worms gravitate toward it and set up home under the sheet.
Of course rats may decide to dig into the fabric (depending on what I use as flexible sheeting), but the whole system is intended to be moved around regularly so that no great pest-nests build up nearby. And it can be laid down over weeds etc to break them down.
Meanwhile I suppose I could peg bird mesh on top of the flexible ground-cover if I really want to exclude rats... But as I'm setting this up away from the chook pens I doubt rats will be a major problem.
It won't look wonderful and it won't be marketable in Bunnings (our major hardware chain). But it should at least turn up some worms! And hopefully the addition of food scraps and worm castings to soil will create improved areas for gardening at a later date.
Now to find a nice flat heavy sheet of something... Rubber matting would be ideal, but old lino might work just as well, with a few lengths of wood (old palings etc) to hold the edges down.
I'll update if this method produces better worm 'farming' than the closed box idea...