Duck Ponds and Fish Ponds… What’s Different? If you have ever seen a genuine duck pond then almost certainly the water looked like thick green pea soup and maybe there was a lot of feathers and other debris collected on the windward shore of the pond. The water in a duck pond, is almost invariably and inevitably green, appears dense and uninviting to all except the ducks that happily swim in the murky green waters oblivious to the desire of the pond owner to have crystal clear water.
Why do duck ponds go green… nitrogen nutrients in bodily waste? Ducks, like you and me, eat to stay alive and move around. In so doing they also create waste products and in the case of ducks these waste products are not deposited into a separate toilet but are involuntarily dispersed into the pond water to act as a nutrient source for algae formation.
These waste products are rich in nitrogen concentrated by metabolic processes occurring inside the duck’s body. Because nitrogen products cannot be allowed to build up in the ducks body the secreted nitrogen finds its way into the pond water and since nitrate chemicals tend to dissolve quite easily the pond water becomes a dilute solution of nitrates.
Dilute solutions of nitrates make excellent fertilisers both on land and in a mass of water. After all that’s what makes your lawn go green in summer. So it makes sense that a pond containing water rich in nitrates will be a kind of heaven for green algae… the nitrates + sunlight to provide energy enables the mass of algae to grow remarkably quickly. The result of profuse algae growth is cloudy water since the algae cells are very lightweight and float to the water surface where they remain to collect sunshine which provides the energy for algae cell replication. Of interest should be the fact that algae causing cloudy water will tend to sink during night time (no sunlight) so pond water clarity should be higher during darkness. Doesn’t really help us since we can’t see the fish in the dark anyway.
So in summary food source (nitrates) + energy (sunlight) results in rapid growth of algae cells which then remain close to the pond water surface in order to collect more sunlight in order to reproduce more quickly and spontaneously. This means so long as sunlight and water and nitrogen (nitrate) chemicals coexist in pond environments then so will green (sometimes brown) algae form.
The way to overcome this problem of green water is to remove the sunlight (impractical in most cases (eg shade cloth), or better still remove the nutrients on which the algae grow and replicate. A biofilter is not designed to remove nitrates nor is a biofilter able to “filter” out the tiny tiny algae cells all by itself. This means the biofilter can only help to remove algae cells if the algae cells are clumped together into larger particles. It is the action of a UV light that actually kills and clumps together the tiny algae cells that makes an ultra violet light successful in clarifying green pond water.
In summary a biofilter alone will NOT cure a green water problem. The solution is to use an UV light (that actually kills the algae) and a biofilter that removes these dead cells that clump together. To ensure an UV is effective it is critical to do 2 things:
Size specification (I should say OVERSIZE for our high sunlight conditions) measured by Wattage is critical… My advice is always to at least double the UV Wattage capacity you think you need based upon manufacturer’s recommendation normally based upon pond volume and exposure to sunlight.
Replacement of the actual UV lamp at least once annually. If you install an UV properly and the pond stays green then like it or not you need more UV capacity so my advice is get at least twice the capacity you think you need by reading the instructions on the product.
If you can’t install an UV for whatever reason then go the natural route of controlling pond algae by using the amazing British product called Viresco… a microbial product for controlling build up of nitrates.
Pumps for Duck Ponds
Because a duck pond, like it or not, is a source of solids debris including feathers, bits of weed and the like the ideal pump to use is what is called a “Dirty Water” pump. This kind of dirty water pump is designed to be able to handle debris such as duck feathers entering the body of the pump. If feathers were to get into the body of a normal pond pump it is possible that they could create damage by jamming the impellor.
Dirty water pumps as they are called tend to sit upright in the pond and suck water and debris into the bases of the pump body. Impellor design is such that feathers entering the impellor are able to pass through without jamming the pump impellor.
However always remember to situate the pump not directly on the pond bottom but say on a brick placed on the base of the pond… This avoids sucking too much sludge into the pond pump which would then find its way into the UV and bio filter.
The following Dirty Water Pumps are best suited for Duck Ponds:
V250 7800L/h, V550 15000L/h, V750 18000L/h.