They can be, but it cost a lot of money, and you need to constantly be monitoring them by testing their urine at home. And if things aren’t going well, you need to get to a vet asap.
Or, you can just feed them the fish scraps that would otherwise be thrown out. Additional fish aren’t being killed, and you don’t need to be worried that you’re causing additional harm to the cat.
This has been a problem in Lemmy.ca for a while and I brought this up on [email protected] a while back:
https://lemmy.ca/post/21634180?scrollToComments=true