I too struggle with pond alga and weeds in all three of my ponds. I have introduced grass carp, tried chemicals, and dyeing the water a deep blue. The dye seemed to work well for submerged weeds, I think the theory is the blue filters out the suns rays necessary for growth but it is not cheap, I had the best luck with the packets not liquid. I rigged up a rake using a piece of 2" pipe about 14 ft. long suspended on chains from boom poles attached to the front bucket of my tractor giving me 12 ft. or so of reach past the front wheels. I welded 10" sucker rod pieces on the pipe as teeth. It worked but keeping the boomers attaching it to the bucket tight was a hassle and the moss and weeds did not just fall off as I had hoped. Someone with better fabrication skills than me (which would be almost everyone) could likely rig up a better attachment method. Good Luck with it, unfortunately if your experience is like mine it is a yearly struggle.