I'm sure the heat and long hours of sunshine has made matters worse and the algae has grown out of control. I suggest filling a large bowl or dustbin with tap water, leaving it 2 or 3 days for the chlorine, etc to wear off first as an emergency temporary storage place for your fish. Once you've transferred them, put on some rubber gloves and pull out all the duck week and as much rubbish as you can remove and drain off some of the water and replace it. Putting in one or two of the small barley straw bales (from good acquatic suppliers) will help in the long term but they do take 2 or 3 weeks to start acting. Probably at this time of year all you can do is emergency repairs until the winter when you can give the pond a more thorough overhaul. If you can erect any form of sun shade over the pond for part of the day, this might help prevent some of the algae. I erect a large golf umbrella to shield my pond from the worst of the sun's rays but it is a very very tiny pond and if yours is large, then short of having a gazebo erected over it for a few days to reduce exposure to sunshine, there's possibly not much practical action you can take.