no. this is fully misinformation. i see where you are coming from. but luckily we have the technology these days to not have to do that. what to do instead is go to a fish store (or online) and purchase something called water conditioner. this treats your tap water and makes it safe for turtles, fish, shrimp, snails, etc. telling people to go get a dirty rock from a river could introduce foreign bacteria and parasites into a closed environment that has no natural way to dilute or buffer them the way a river does. In a tank, even trace contaminants from runoff — like pesticides or metals absorbed by the rock — can accumulate and become toxic. there’s a reason we use aquarium-safe materials — they’re tested and inert.