This may be too simple and may have later adverse effects, but I cleared my one year old pond last year by throwing two barley straw bales, broken up into mats about 6" thick. It took about two days of it floating around with the wind for the sediment to adhear to the mats, but it worked. Mats eventually sunk and I think are good for creating a 'food chain' for fry. Yes/no??
Not real technical, but worked for me. I routinely have a ph of 7.8-8.4 (depending on time of day), hardness of 40, and alkalinity of 50-60 without adding anything.
No adverse effects will come from the barley straw used. The bacteria grown to decay the barley will provide a good base for the food chain as well. Too much organic decay could deplete oxygen though.
