Would you define earthworms as pets? It is probably a stretch to do so, yet I am very fond of the earthworms in my two worm farms.
The worm farms take all our 'green' food waste, including vegetable and fruit scraps, tea bags and leaves and coffee grounds, and turn them into beautiful, dark worm castings and worm 'juice' that, when diluted, makes a fantastic liquid fertiliser.
I have two commercial worm farms, a rectangular one and a round one. I have had them for at least the past decade and they continue to work beautifully. About once a week I add a handful of lime to neutralise the acidity of food scraps, but that's about the only maintenance the farms require.
I once killed off my entire worm population during one of Adelaide's severe heatwaves, so I now bring the worm farms into the laundry if I think we are going to have a run of extremely hot days. The composting worms are quite expensive to buy, so killing them off is not a good idea.
I love my worms so much that when we moved to Adelaide I brought tub of my Melbourne worms in the car.
My goal for next summer is to produce all the garden fertiliser I need on site. I hope to use a combination of compost, chook poo and of course, the wonderful castings produced by my composting worms.