Comment by Alex3917

You actually don't need especially sterile conditions to grow oyster mushrooms. I've done this tek, it works pretty well:

https://courses.biology.washington.edu/biol440-spr16/folders...

Also the mycelium has a pleasant almond smell, so that's a nice whenever you go downstairs to check on them. The hardest part is figuring out what to tell the Petco employees when they ask what kind of cat you have.