Vegetable (Veggie) BioFilters For Goldfish and Koi Ponds
Most pond plants with submerged leaves produce considerable oxygen during the day. Underwater freshwater garden pond plants reduce nutrients on which pond algae feed. Using this principle it is possible to create natural bio-filters that can do the job of a man-made biofilter although it is probable in heavily stocked fish ponds that you'll need a man-made filter rather than rely totally upon a planted filter or vegetable filter. The veggie filter is especially useful in removing nitrates (consumed by the veggie filter as fertilizer)
Vegetable BioFilters ... Aquatic Plants For Gold Fish and Koi Ponds
The idea of using vegetable filters (also called veggie filters is an area where
plants are deliberately grown en masse) to remove algae for Nitrate control and
green water control is not new by any means. It has found use in systems where
people do not want or cannot afford UV systems.
Concerns expressed about vegetable filters include blocking of pump impellers by stray roots and leaves. Some plants would be worse than others ... eg water hyacinth. Despite this they are excellent nitrogen removers.
An ideal plant to use is Azolla also called Fairy Moss. It grows extremely quickly and is capable of removing large amounts of nitrogen and of course carbon through photosynthesis. It is also easy to remove simply by netting in the event it over-runs the filter area.
Duckweed is another plant that can be used for this purpose as well as being an occasional food and dietary supplement item for gold fish and koi. Water cress has also been used very successfully ... in fact any quick growing leafy plant is good for this purpose of converting nitrate, phosphate and carbon into bio mass.
This (image above of veggie filter) is how a vegetable filter could look when finished and planted. It shows the basic principles of a vegetable or mini reed-bed in action
Plants For Natural (Vegetable) Pond Filters recommended by Peter J May
The Norfolk reed (Phragmites australis) is by far the best since it not only removes pollutants but is capable of adding oxygen to the water ... ie it is an oxygenator plant too. Oxygenators are generally those plants whose leaves are always submerged so that oxygen from the photosynthesis process has a chance to dissolve before being lost to the atmosphere.
Other useful plants are generally in the fast growing class so that maximum biomass is created in the quickest possible time. Consider the following ...
- Sweet Galingale (Cyperus longus)
- Soft Rush (Juncus effusus)
- True Bulrush (Scirpus lacustris)
- Flowering Rush (Butomus umbrellatus)
- Water cress has also often been used
Here's an extract from a Peter J May article ...
The common reed or Norfolk reed, Phragmites australis, is the top performer in these filters, because not only has it got a phenomenal growth rate in the right conditions, but also obligingly oxygenates the water as well; essential for many of the bacteria that need oxygen to sustain them.
Other plants that do well in my books are Water Cress, Rorippa nasturtium-aquaticum, although it succumbs in very polluted water, Bittercress or Cardamine praetense and Fools Water Cress, Apium nodiflorum, which loves alkaline water. (TRANNIE 4: Water cress: Rorippa nasturtium-aqauticum.)(TRANNIE 5: Bittercress, Cardimine praetense) (TRANNIE 6: Fools Water Cress, Apium nodiflorum; the rampant root run is revealed, sprouting at virtually every leaf node.)
Is it easy to add to my vegetable pond filter system?
Its as easy or difficult as you wish to make it.
If you already have a stream, or waterfalls with header ponds, you can place aquatic baskets planted up with cress or reeds in strategic places. In fact any plants that are easy to keep in order will help.
Keep an eye on them in order to stop them from seeding or running adventitious shoots under your rockwork. A regular cut back ensures they are kept working producing new growth most of the season. In the header pond to the waterfall I found Villarsia, Nymphoides peltata, a useful vegetable filter.
If you have a relatively small pond and you would like to buy a proprietary product off the shelf in kit form with everything you need, then there is the Oase Filto-Fall, which is a basic kit for processing the water in a 2 cubic metre pond. All it needs to work is a pump that will turn over 5000 litres per hour, which needs a power supply and hose, and of course half a dozen clumps of Norfolk reed.
Oase Filto-Fall .
It is designed to sit embedded into the ground on the edge of a pond or at the top of waterfall or stream. Water pumped up from the pond will enter at the front base of the tank- note the hole for a fitting in the bottom /front- and rise up through the plants and cascade into the header pond. Because it rises up in the tank from pressure from the pump, it could not be incorporated in an existing filter system unless it was of the pressure type like the Hozelock Bioforce or the Oase Filtoclear filters.
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