Natural pebbles for fish aquariums. All stones are graded to approx 1/4 inch. All stones are basically the same size. Will not clog filters like sand. Natural, tiny river pebbles help create a healthy fish environment. Helps promote good bacteria to maintain good water quality. Tiny pebbles have random colors and shapes. Your fish will feel comfortable with these natural river pebbles. Nice natural looking pebbles. Rocks are rinsed and dried before shipping. Shipping can cause dust; Please rinse again before use.