I have the same problem this year, my algae bloom is due to cinder block dust (we're under constructions) getting in the water. I have a lot of plants, but obviously they're not doing well with the higher ph caused by the dust, (that's why the excess organic matter in the water) and I'm not about to start messing with altering ph chemically, so for now I just scoop up all the algae I can, keep the mechanical filter clean and feed the fish less.
I did a 20% water change when I realized what was causing the algae bloom and since then we've changed the location where we cut the blocks and the ponds are starting to recover.
I hear many people complaining of string algae this year, people who never really had this problem before and cannot figure out the reason why
I usually get very little and only in the plant pool, in mid season when the plants begin to fill and slow down the water flow, like last year I realized my water Hyacinth were taking over and as soon as I thinned them out the water started flowing freely and the algae were gone
Sometimes 100% clay kitty litter hung in a fine net bag can help clear some types of algae. I need to do that again as I have it in my plant pots but it's kinda old now and does not really circulate well in a pot. The litter can cloud the water at first but it will go away after a bit.