Is fish excrement pure or impure, and if it causes the water in the fish tank to become turbid and change color, is this water pure or impure if it spills onto the ground?

The excrement of fish is pure, and a fish tank is considered pure. If anything falls from it onto the ground, it does not contaminate it, because fish waste is pure. If there is doubt about the cause of its alteration, it is considered pure, because the default state is purity until impurity is established with certainty.