Art by Alexander Vasiljev, Copyright © 2017


Friday, July 25, 2014


Continuing my ongoing trial and error experience with the pond, I thought, why not watercress? I am still looking for more ways to lower nitrates, besides 100% water changes.

Right now, the pandanus plants (Pandanus amarillifolius) that I have been growing in the ranchu pond are flourishing. I bought two kinds -  tissue cultured small plants eight months ago (see my post "Pandanus Plant") and an adult pandanus 1.5 foot (45 cm) tall, that I divided on three pieces. New roots are developing well and judging by the new growth and color, the plants are getting enough nutrients.

Pandanus plants growing in my ranchu pond

The water is drained to show pandanus root system

To extend my nitrate "elimination", I am now trying out watercress (Nasturtium officinale). This plant is aquatic or semi-aquatic, naturally found in and around freshwater streams. I thought that watercress would be a perfect candidate to grow in my ranchu pond. Being a popular leaf vegetable in my kitchen, I am also looking forward to consuming it.

I started off by germinating watercress seeds in finally cut paper towel. Keeping the substrate very wet was the key. Why cut paper towels? I try to avoid introducing pathogens and any other unwanted elements into my ranchu pond. Any plant's root system that had been grown previously in the soil, I sterilize with bleach. Cut paper towels offer a clean substrate.

After the seedlings developed 2-4 true leaves and a root system, they had been transplanted on pieces of Matala filter media, which I have been using in my bio filter. Matala mats seem to be a perfect medium for using in my improvised hydroponic culture. I hooked strips of Matala to the edge of the pond with hooks made of galvanized wire, so the strips are halfway in the water, allowing only the root system to be submerged. 

Fifteen days later, my watercress plants are growing well. With little time, their root system will come through the Matala mats using up the nitrates and growing succulent leaves for my kitchen.