Marco Schwarz wrote:
Hi..

This is a great inexpensive plant to put into your fast
flowing water such as waterfalls. I bought some last year
at an Asian supermarket with sharp leaves.

Google the following two plants:

# Nasturtium officinale
# Armoracia aquatica

Is your first (second) Watercress one of them?

Is one variety better for ponds than another?

The European Watercress Nasturtium officinale is emersed and
from time to time flooded easy to keep. In the wilds I saw
it several times submersed in cold water wells and creeks
streams. That might possibly depend on temperature,
minerals, KH, CO2..

Your Water Horseradish (Watercress) Armoracia aquatica is a
great water plant, too.

The "Nasturtium officinale" is what I used last year.

The "Armoracia aquatica" is what I have recently discovered and will
try this year as it has a more brilliant green colour.