Rainwater has been used for this test.
On running water or ebb and floww the EC can be put up and controlled.
Growing on non-running water, this isn't possible.

Rococo 8 weeks rooting
in peatmoss        running water

Rococo 3 weeks rooting
    running water     non-running water

After 6 days vase-life test
running water         non-running water
Controlled EC   Non-controlled EC