Hey, Albert. You might get better results using a skim mix of cement with the algae. It will still rot fairly fast but that is why it makes a good mulch or addition to the compost pile.

This poster found an intriguing use for string algae. I'm going to try this one myself. (Hope this link works!) http://www.americanponders.com/forum/index.php?topic=10403.0

Algae control is as easy as A-B-C 1,2,3 - R Calcium bentonite [Koi Clay] works very well at killing and suppressing algae growth, but first: 1. If your pond has a gravel bottom you may need to debulk the nitrogen and phosphate load first by pressure washing string off of the side wall rocks and and the using lower pressure with more volume to wash the muck down to the lowest level where you can sump pump it out to the benefit of your gardens and trees. I did this in early June [after a few year's hiatus] and my ponds water has remained nearly crystal clear since, just from that. 2. After your water has stabilized, ~ 24-72 hours, depending upon your filtration method, you may reintroduce your Koi, and resume normal feeding cycle, using extra caution to avoid overfeeds, prevent over wash heavy rains, which can raise nitrogen and phosphate levels. 3. Then you must decide you methods for long term string algae control. control that and you won't have any of the other stuff in significant amounts to worry about. A. Netting, removes string and removes its incorporated nitrogen and phosphate out of the ponds biochemistry. If you wait until you have a lot it is hard on your back and the results are as a whole unsatisfactory, but it is easier to debulk living string or blanket weed while it is a live and buoyant, than after it has sunk to bottom and is doing a good job of starving your Koi of critical oxygen. So, net what you can and kill the rest, while upping your preventative methods. B. Chemical algaecides [non copper containing, so that snails and crustaceans remain unaffected], not only kill visible string algae, but its spores and initial growth Sodium carbonate peroxyhydrate essentially harmless to plants, fish, and other aquatic fauna is spread over the surface wherever filamentous [string, blanket] algae are found and sinks down onto their strands for a very potent contact algaecide, but as it dissolves does and equally good job on planktonic free floating single-celled algae which cloud and color water green, ultimately turning your pond's water into thick pea green soup, if you nitrogen and phosphate levels are high enough. PAN [Poly(oxyethylene) (dimethylimino) ethylene (dimethylimino) ethylene dichloride], the active ingredient in Algaefix, though it must be used with some caution not to overdose or you may lose Koi. Some web essayists have made much of the LD50, of Algaefix, and it is important to remember this when using the product, but the LD50 of many therapeutic drugs necessary for survival with some diseases is not much different than Algaefix for your Koi. If you must use, use wisely! C. Calcium Bentonite marketed as Koi Clay at /substantial markup/ is mined as diatomaceous earth and proves toxic to both filamentous and planktonic algae and also serves as a flocculant binding small debris-particles which then sink to the bottom or become processed by the specific biofilter utilized. Calcium and other trace elements found in powdered calcium bentonite improve Koi color and plant health, such that the ponds circulation and natural nitrogen cycle provide everything your fish, small creatures like frogs and snails, water lilies, and other aquatic plants require to grow. Making the addition of plant 'fertilizer' unnecessary and counterproductive visa vie the algae issue Remove dead aquatic material and debris before it breaks down and enters your pond's Nitrogen cycle, or you will have plenty of string algae to remove later, no matter what you do. Happy Ponding!

Yes it's 3% and effective. Stick with the H202 and leave the chemicals for those who don't mind draining their wallets. As rsingley pointed out, better to correct the underlying isssue than to treat symptoms.. @ catherinet, yes.you.can. have both! I don't recall you having a problem with string algae? Maybe I missed it. (I refuse to concede it might be my memory, lol & I did stay away for a bit). I used to wonder what was this stuff called string algae others were battling, until.... my tiny waterfall was suddenly covered with it, seemingly overnight. Never saw it comin'.. Fortunately, I was armed & dangerous thanks to the experienced ponders here. My pond was several yrs old by then so I had lots of ammo, lol. I shut off the water fall, doused it with H2O2, then waited a few minutes for it to do it's thing & rinsed with the garden hose. I did remove some by hand before rinsing & just tossed it around some nearby terrestrial plants. As you have discovered, it's full of nutrients & makes for great fertilizer. Never encountered it before or since in my pond but I've dealt with it in friends' ponds. A healthy balance is key to keeping it at bay. Never did figure out why it appeared in my pond that one year as the pond was well established by then, well maintained & nothing had changed. I'm just thankful there's been no recurrence! @ jacob12345: please kindly cease & desist from peddling your wares here. blessings all around, ~digger