I've always been curious about the advice to use kitty litter in
aquaria. It's a totally uncontrolled product - there are no
standards for it at all. Some include glues to make the stuff
clump when wet, others contain unmentioned stuff to allow it to
soak up liquid better, others chemicals to deactivate our sense
of smell ... Further, it's intended to be disposed of after use,
not used for anything else. It can contain absolutely anything!

Personally I buy only things that are rated fish safe. Even then
I still get stung occasionally (like the Jungle Labs fungal
treatment I just used that cleared the fish fungus fine but
killed off all the Brazilian elodea while leaving other plants
untouched!)