hi we have recently put in a couple off large outdoor ponds one of the ponds as off the last month had a rather brownish in colour and slimy in textur in the pond the water all though is nice and clear and the fish and plants are thriving but this stuff is blocking every thing up we have to clean all the filters every we have a large stone filter also a filter on the fountain and another filter on the pump witch lifts the water for the water fall we have tried pond blocks and some algae killer with no succes could anyone help out as some advice would be good berfor i fill the ponds in again (lol joking about that bit ) cheers and merry xmas to all herb

Where do you live? How old is the pond? How big is it? There is brown algae which is actually diatoms. It's easy to remove by hand and shouldn't clog any filters. Since you have something clogging filters, it may be hair algae or some other sort of algae. It's normally green but could turn brown if it dies. The brown stuff could also just be degrading pond debris (dead plant material, dead algae, etc.) which can be slimy and jam up filter intakes.

I never use algaecides in my natural ponds. My page on pond algae should give you some ideas if the problem is algae:
http://www.fishpondinfo.com/algae2.htm

If it is an algea problem, this might help a little if you haven't done this yet. Add more plants if the vegitation is scarce, and throw in a half dozen or so of Japanese trap door snails. I found that when I added snails, the offspring clung to the filter screen and ate the organic debris that got stuck there, and the adults scouraged the bottom picking up everything else, especially in the summer. And because I had so much nitrogen in the pond (thank you Satori Clarity Max), the plants exploded once they got climatized to the pond. The plants may have to wait a couple months for the weather depending on where you live. The snails are pretty hardy though, and you can add them fairly soon.
A note on microbe lifters. With some products I found that the water darkened before it cleared up. Don't panic if it gets darker when you add anything to it, wait 24 to 72 hours, then start to worry again. Also, once I added the microbe boosters, the filter would plug up fairly quickly, this is a sign that organic material in the pond is being broken down and caught by the filter.