Ecology of the Planted Aquarium written by Diana Walstad is one of the books which inspired me most for low-tech natural aquariums. Diana Walstad explains why emergent plants are better water purifiers than the submerged water plants as follows (in chapter 9, the aerial advantage):

Umbrella papyrus (Cyperus alternifolius) in a lowtech natural aquarium (see biotope in my room)

Umbrella papyrus in a lowtech natural aquarium

In comparison to fully submerged plants, emergent plants are characterized by:

  • Much faster growth (in terms of real growth measured by dry biomass)
  • More efficient use of carbon dioxide (CO2) and light (aerial CO2 is not limited by the dissolved CO2 in water)
  • More efficient oxygenation of the root area
  • Enhanced biological activity in the root masses of floating plants

With emergent plants, or plants with the aerial advantage, Walstad means all sorts of plants whose leaves are not submerged in water. These can be land plants, amphibious plants like Anubias and Echinodorus species, floating plants like duckweed and water hyacinth, water plants with emergent leaves like water lilies and lotus.

Emergent plants receiving preferably natural sunlight can purify water much better than the most high-tech manmade filter can do. The faster a plant grows the faster it purifies water. Keeping emergent plants for water purification is almost mandatory in order to keep sensitive fish like Apistogramma species. The services of emergent plants can hardly be replaced by hightech filters and tedious maintenance work like frequent water changes.

Besides amphibious plants like Anubias and Echinodorus species I use a number of common indoor (room) plants in my aquariums for water purification. That is, for reducing all kinds if organic and inorganic contamination such as ammonium, nitrite, nitrate, phosphate etc. You may find below an image gallery of these plants. Most fast growing and robust indoor plants suitable for hydroculture can be used in aquariums or tropical ponds for water purification.

Most common indoor plants used for water purification in aquariums:

  • Golden pothos (Epipremnum pinnatum, syn. Scindapsus aureus)
  • Umbrella papyrus (Cyperus alternifolius)
  • Climbing fig (Ficus pumila)
  • Split-leaf Philodendron (Monstera deliciosa)
  • Lucky bamboo (Dracaena sanderiana)
  • Syngonium species

The vigorous Monstera deliciosa, a kind of creeping vine, is one of the best water purifiers among indoor plants which needs but lots of space for growing. I tried every plant in the list above except for Monstera deliciosa with good results excluding the two Syngonium species I had kept.

I can highly recommend Golden pothos (Epipremnum pinnatum) for every aquarium lover. It is robust and adaptable, and it grows fast. Its dense roots look very natural and decorative in an aquarium providing hiding places for shrimps and small fish. It can easily be propagated vegetatively by just cutting side shoots that can be put in a vase filled with water. The roots will appear in several weeks. You don’t even necessarily need a hydroculture pot for inserting the plant in an aquarium. A piece of Epipremnum pinnatum attached to the side glass will soon grow roots in water (see the related picture below).

Umbrella papyrus is an excellent plant for large aquariums and ponds. Under natural sunlight it may grow as high as 1.5 meters (5 feet). It can be planted directly into the bottom substrate provided that the water depth is less than 40 cm (16 inches). It is a robust and fast growing species. As a fast growing plant it keeps the bottom substrate healthy through its vigorous network of roots. It is a perfect water purifier water Malawi and Tanganyika tanks because it can easily adapt to higher pH degrees.

Climbing fig (Ficus pumila), also a most robust and adaptable species, is a slow growing but persevering plant like Anubias. It may take years to grow, but once grown, it is a very decorative plant and a perfect water cleaner. Given time, climbing fig can cover the back wall above an aquarium. It can hold and grow much easier if the wall is covered with a cork plate.

Tunç Ali Kütükçüoğlu, 18. January 2010, Zürich