orange/brown slime in pond ...help!

Hello,
We have a stream that runs into a largish pond and out again through the bottom of our garden. It has been getting orange/brown sludge that will spread if undisturbed. This can be broken up with a rake and dispersed but it returns a few days later. The main source seems to be 2 drainage pipes that run from our garden but it also gathers around the edges of the pond that aren't near the pipes. I am a total novice (its our first home and first ever garden) so I don't want to do anything that will disturb the fish in the stream, but I also don't want to leave it incase it is doing damage to the pond. I am guessing it is a form or iron bacteria but I can't find any information about what to do about it. Does anyone know if I need to treat it or is it harmless to the wildlife?
Many thanks

Posts
Whatever it's doing it's probably been doing it for years. My guess would be rusting iron pipes from higher up the drainage system. or, if your area is largely sand/gravel, staining from that. Some of the field drains around here are bright orange from outflow from the gravel washing in the gravel pits
In the sticks near Peterborough
Hi CustardKat. I have a similar thing in my garden. If you type "orange moss" into the search box the thread will come up. Lots of good information from peeps on there. Hope it helps.
You beat me to it Plant Pauper - here's the thread http://www.gardenersworld.com/forum/problem-solving/orange-moss/827717.html
Hope that helps
Gardening in Central Norfolk on improved gritty moraine over chalk ... free-draining.
Thank you for all your help, I hope that it isn't harmful to all the creatures in the stream.
My pond, sheugh, garden and surrounds are all hoochin' with wildlife of all descriptions. You'll find that if creatures don't like it they'll move but they'll be replaced by other creatures who think they've found heaven!