ElGringo

If you buy a UV system, you need to clean it every 2 weeks to keep it working. Oase sell a system with inbuilt magnets that help kill unicellular algae. When you have blanket weed attaching itself to everything, the best thing is to feed the fish a lot less (once a day is a max.) and to shade the pond. Lots of plants, especially rushes, absorb phosphates (this is the major cause of algal blooms) ashtonishingly quickly.

If you have a small pond, (<6ft, 6ft, 2ft) avoid Elodea densa or Elodea crispa, (so called 'pondweed'), they grow and smother everything. Ceratium is a floating plant that produces algicidal chemicals, but again needs to be thinned out every week. In my pond I harvest them to chuck on the compost, if you let them rot away in the winter they will release nutrients straight back into the pond, which the algae will utalise next year. I also have a 6'' layer of anoxic mud in my pond, it harbors bacteria that reduce nitrates to nitrogen, which disappears into the atmosphere.

Barley produces algicidal chemicals, but if you attack the source of the problem, nutrients and sunlight, with careful planning and use of water plants, it will be a permenant and attractive solution.

In the UK it's a problem, you're not allowed to remove frogs, newts or any other native fauna that set up home in your pond. Don't try to kill them, our native wildlife has almost completely disappeared and you could get lumped with a hefty fine. So, I built a stream running into the pond, and all the frogs go and live there instead, and don't hassle the fish.

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Richard