Green water / Blanket Weed


Just wanting to know what people use to help clear there Blanket Weed / Green Water in their ponds over the summer and if they add anything do you do it before any outbreak or after ?

Have you found using an overrated UV filter cures all problems and you never have to add any additives ?


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Hi Mark,

My pond is roughly 9ft x 8 ft. and I don't have a pump or a filter. It has goldfish, frogs and newts.

I use barley straw to help keep down blanket weed. You should carry on using it all year round and it'll take a little time to kick in ititially, but you must then keep it going or you'll have to start from scratch again. The instructions tell you when to replace it, but I do it more often and leave the old one in for 6 months to carry on working. It's when the straw is breaking down that it starts working.

I initially bought two pouches which come in mesh bags, but I also now use the green mesh bags that oxygenating plants sometimes come in and fill them up with barley straw from a sack bought in a pet shop, which is much cheaper. I use corks (good excuse for a bottle of wine!) so that I can fish the bags out later, rather than have them disappearing to the bottom, never to be seen again. I shove mine under plants I have on the surface around the pond because the straw can look a bit unsightly till it starts to sink when it's breaking down. Make a note of the date you last added a new pack on your sack, then you'll be reminded when to add another one.

Regarding green water, barley straw should also help with that. When I first built my pond a number of years ago, I used to think the water would never clear in spring, but I rapidly realised that all ponds 'cycle' at that time of year and mine clears itself over a few weeks. It's a natural process. How big is your pond?

Don't know if any other members have any more information for you, but hope this helps.
Big Kid

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