Central South Island > Hunting News April 2008

Filamentous algae and a simple “cure”.
Graeme Hughes, Fish and Game Officer.

Low water plus sunshine equals “slime”. Over the years this complaint has become more common. Duck ponds are cleared, vegetation pruned and the hide refurbished. The pond and its surroundings are looking great for the approaching season. Almost overnight the water becomes an environment for a green “slime” which very rapidly can cover the entire surface of the pond, especially if the pond is a shallow one. This common green filamentous algae is usually the result of long sunshine hours and some form of enrichment, be it animals or fertiliser, two common causes. As the algae becomes thicker Mallards tend to avoid it until they abandon the pond altogether. Raking the pond is a back breaking task and only a temporary fix.

As I remember from reading an article several years ago, a farmer was carting bales of straw from a harvested barley paddock to a storage area. The route to the storage site passed by several small ponds, generously covered with green “slime”, filamentous algae. As is often the case the occasional bale of straw topples off the trailer on the journey. One wayward bale landed near one of the  ponds coming to rest half submerged at the waters edge. The bale of straw remained semi submerged for sometime the exact duration I cannot recall. However the farmer soon noticed that the filamentous algae disappeared on one of the ponds, the pond with the now very soggy runaway bale of barley straw in it. Apparently an enzyme in the barley straw kills off the algae.

A duck pond owner in the Haka Valley was most disappointed to see his pond become very green with algae which soon dispersed the few regular mallards which visited in the evening. He related how he manually cleared most of the pond with a garden rake but this only made way for new algal growth.  At my suggestion he obtained a bale of barley straw. Because the pond was shallow the bale was broken up into smaller portions and scattered around the pond. It sure looked a mess but within 20 days the problem was solved. This is the first year he has not fed the pond with grain and the first year he has experienced massive growth of algae. What was he feeding to the ducks in previous years? Barley of course.  He is now feeding small amounts of barley as an “algae preventative” and now the dozen or so Mallards have resumed their visits bringing a few friends along for the experience, an extra 90 birds at the last count. 

back to Both Barrels

If you would like to be kept in touch with Gamebird hunting news and other hunting information, please sign up for Both Barrels, our Gamebird hunting email newsletter.