Floating empty Coke cans in a pond will kill string algae. The red color of the can reflects the blue spectrum of light required for the initial vegetative stage which algae need to grow. Tie a string to the tab and a weight to the other end of the string. The length of the string has to the same as the pond depth where the can is located. Fill the can 3/4 full of water and then tip over in the pond so 1/4 of the can remains full of air. Space the cans 12" to 16" apart in the pond, in a grid pattern.
Now all I need is a few readers to believe this, try it, or say they tried it, and post that it works.
Anyone interested in actual solutions?
For streams and waterfalls...put the pump on a timer. If you're at work all day and no one is home make sure the pump is off. Off all night. Existing string algae will probably stay around, but only getting water for a few hours a day... that will put the hurt on it. Or clean it off. It'll have a really hard time coming back when the water only runs for a few hours. You will never have any string algae in a stream or waterfall. Of course the stream has to be built to drain completely. But even if not, greatly reduced growth.
If you think waterfalls and streams are needed for O2 buy an air pump and have the timer turn it on when the water pump is off. Air pumps are in the $40-70 range and consume about 5 watts. Timers are about $15 for simple and about $150 for way cool remote multi-outlet programmable deals. Air pumps are way better at putting O2 into the pond. You'll also save about $50 in electric each year so pay back is about one year. Plus you'll save wear on your pump...the cash is just rolling in.
Waterfalls and streams are great filters so you'd lose that. Build a Trickle filter. Just a pile of rocks with water running over it. Does same thing as waterfalls or stream just in a smaller footprint. Most people don't mind string algae on it. Or the filter can be hidden. And besides, string algae may kill green water algae, so imo control is better than elimination. A bog filter would be another option.
Inside the pond...Manual removal. The biggest issue here for me were pots of plants. Just impossible. In an empty pond manual removal can be really fast, like 10 minutes once a year. I had the pots in the pond once upon a time. The string algae made it an ugly mess. My solution was to move marginals out of the pond. Never had string algae in the plants again. All these plants do better outside and at or a bit above the waterline.
Only lilies have to be in the pond. Worst case, cut off the leaves and remove the algae. The leaves will be back shortly. But I can't remember having a problem with string algae in the lilies.
Once the pots are removed...Most people don't mind string algae in the bottom of the pond. But it can fill a pond. I take 2 sticks of wood, maybe 1.5" square and 4 or 5' long. Nail them together side by side, a single nail right in the middle. Now they can open and close like giant salad thongs. And we have the salad. Open them a bit and plunge into the string algae. Close and start rotating the sticks, like spaghetti on a fork. Depending on the species every bit of string algae will wrap around that ball, an entire pond's worth. Pretty impressive, very satisfying, but can be heavy to get out of the water. I'd forget about composting string algae...really slow to decompose, and you have that huge ball. But you can try.
Some species do attach to liner and rocks, but these aren't the long growing kind. These should be loved.
No algae allowed at all... You're talking about serious chemicals like potassium permanganate, used on a regular basis.
Easiest, almost no effort, no chemicals (in the pond)... Wine. If you still care about the algae increase dose.
