Freshwater planarians
We usually find planaria on the stones bottom surface, in lakes, rivers and beaches, most of them -and easiest to collect- on shallow waters (10-100 cm).
Sea planarians
We find them in rocky beaches, under sea-wet stones, usually covered with seaweed. Their distribution is erratic -in some beaches there might be thousands, in the next one none. When the tide is down they are easier to find and collect since they stay still under isolated, water uncovered stones.
Forest planarians
In highly humit woods, under rocks or sleeves. In Spain they are found mainly in the Atlantic sea -affected northen woods.