slime and grass in pond

[Devynne]

We have slime and weed growing in our large pond.(small lake) . The weed is very dense and tangley and has a slimey top and is a light green. It grows from the edge of the pond out to about 20ft from shore where the water becomes deeper. Deepest part is 30 ft. the pond is about 1000ft by 100 ft. What can we do to remove this weed please. We have tried Bales of rye, straw and salt and nothing has worked.very frustrated! any suggestions will be appreciated..thanks

[Upforit]

Is it 'stringy' and reminiscent of sea weed? It sounds to me like it is blanket-weed. If this is the case, the only thing to do is physically remove the weed regularly. It won't get rid of it, but can be managed this way. I have a pond in my garden, much smaller than yours and the weed appeared two years ago after 13 years. There are proprietary weed removers specific to this here http://www.koicarp.net/water_treatment/no_more _blanketweed.html
and here http://www.pond-doctor.co.uk/longevilweed.htm
but I cannot vouch for them as I do not use chemicals anywhere in my garden. My research, on a balance of the information available, led me to believe that there is no way to control this weed other than manual removal.
With reference to using straw, in case you are not aware, it is barley straw that should be used for cleaning ponds. Other straws do not work. If you didn't use barley straw, maybe you should try it although again I cannot vouch for its ability to control blanket-weed.