Also not a good idea. Using "products" for the toilet water will leech fumes into the fish tank and kill them. The bathroom is not a good place for fish since a lot of toxic cleaning products are used there.
And yeah. I kinda agree here. It's a bit too creep-tastic for my liking.
Seperate tank, and chemicals aside..... I'd never want to flush it. I don't think I could do it.
Like..... especially at a 2:30am bathroom run, when you are 1/2 asleep. Talk about a fish keeper having nightmares.