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!

The issue with barley straw is fairly complex. It's not certain exactly how it works. If it was nothing but the release of low levels of hydrogen peroxide then it would be possible to set up a chemical dosing pump to add very small volumes over a long period of time. Although there are numerous discussions on the topic, that it has been researched in Great Britain, etc. -- there does not seem to be a single, peer-reviewed scientific paper where they have actually measured what it is released (and there are some exceptionally sensitive assays for peroxide and peroxide metabolites out there). The website below presents a discussion as to what may be going on, where they have conducted side-by-side studies. However, it too is not a peer-reviewed scientific study although several papers are cited (they do not have any measurements of what is being released). Regardless of all of that...adding barley straw is, as far as I am concerned, another of those "do no harm" things. You can add it and it may help. It won't hurt unless you decide to carpet your pond in barely straw!!! :-)) As to using vascular plants (water hyacinths, water lettuce, etc.) --- these will do double duty to provide shade and act as a phosphorous sink. You can help them to compete against the algae by adding no more than 1/2 tablespoon of potassium nitrate per 1000 gallons once a week (it goes under the name of "tree stump remover" in most gardening centers - if in doubt ask for the MSDS sheet on the product which they are required by law to be able to get for you). The use of water hyacinths, water lettuce, etc. will also provide a very large surface area/root mass which will harbor a variety of "critters" such as daphnia that will go after the algae as well. Hope all this helps. ---David Here is a link that might be useful: Link to Purdue University, Dr. Lembi article/discussion

If your water hyacinths are not doing well at this time of year I would suspect they are not getting one of the necessary nutrients. If they aren't growing well they can't remove the phosphate that fuels the algae. If you can figure out what they are deficient in you can add that nutrient and they will resume growing. If the hyacinths are sort of olive drab in color with long root systems they are probably deficient in potash. If they are a sickly yellow with veining on the leaves and a lot of dead plant parts it is probably an iron deficiency. In both cases there will be smallish plant tops with few new plantlets. If you can fix this your algae problem will diminish because the hyacinths will again be able to use the phosphate.

Every time I clean out my UV pressurized filter, I collect the "waste" in a 5 gal bucket I use for the final rince for the filter pad. I then either dump the waste into the flower garden, or whatever tree looks thirsty. Everyone seems to be happy. I DO NOT add to my wifes tomato garden though. 1. She would kill me. 2. I add chemicals to the water everyso often, and don't think I want to eat them!