…was just one of various bemused comments from visitors about the orange mesh bag – actually full of barley straw – currently breezing around on the surface of my pond as part of my battle against blanket weed and green water.
Wiggly Wigglers (www.wigglywigglers.co.uk) sell bags of straw in trios (they are on special offer as I write, the prime time for putting the bags in ponds). By the time it is settled in and starts to submerge a bit, the combination of sunlight and water temperature will make the rotting barley straw release hydrogen peroxide (I think) into the water, which inhibits the growth of algae. You can undoubtedly Google some better science on this.
What no one seems to latch on to though is the fact that as soon as they become saturated, the bags sink – out of sight (which is a bit of a relief, actually) , but more importantly out of sunlight – which slightly ruins the whole operation. So I always open up the bags, stuff a small empty sealed plastic bottle right in the middle, compress the straw around it so that it is invisible and then seal the bag up again. The bags (which, by the way, do fade quite quickly in the sun) remain permanently partially submerged. Hey presto. Drowning old ladies in hairnets in my pond.
Does the barley straw technique actually work? Well it undoubtedly helps – as long as you hoik out the worst of the algae if it starts to accumulate (if, for example you have to top up your pond with tap water, which encourages algal growth). But it also helps to allow between a half and a third of the pond to become full of oxygenating weed.