Murky water in Pond

Have a wildlife pond and last year could not get water clear. Tried oxygenating plants and barley straw. Pond is 4ft x 5ft  approx and have added 3 oxygenators  do I need more? 

Is it located in full sun ?

Yes

There lies the main problem - the sun !!

To improve water quality you must shade more then half the surface water from the sun. You need a good selection of pond plants  like marginals, deep and floaters to help you. Tall planting schemes around the front and sides of the pond will also help cast shade onto the surface.

The link below which I contributed on has more info - you may find useful as it holds more info. There is also another but I'm unable to find it, when I do I'll post it onto this thread.

http://www.gardenersworld.com/forum/problem-solving/pond-lacking-in-oxygen/2678.html

I have recently bought a solar powered, floating pond pump, which was only £15 (good old eBay) and it is doing a good job of aerating my tiny wildlife pond - before I had it, it used to go stagnant quite quickly, which meant a lot of work with buckets and water butts to get rid of the stagnant water and replace it with fresh rain water.  Now it seems to be stable and doesn't smell bad anymore.  It also means that when the sun is shining on the pond, I have a little fountain, which the birds sometimes wash under.  The pump just stops as soon as the sun goes in or at night.  Might help?

I use a solar fountain in my wildlife pond too which keeps the worst of the blanket weed down, though I still have to twirl a stick occasionally, until the waterlilies leaves start spreading, after that the pond is fine without the fountain.

I'd get a bag of daphnia or water fleas from an aquatic store and add them. They eat greenwater algae and bacteria as long as they don't get eaten by fish or damaged by pumps. They breed quite quickly but they'll take a bit of time to conquer it - perhaps a few weeks. The more you add, the faster they'll tackle the murk. As with most wildlife gardening, it's the base of your trophic pyramid that's the most vital.

Watercress is also a fantastic native biological control which will grow from cuttings, or more usefully, supermarket bunches. Remember that submerged plants won't grow well in murky water due to low light levels, so as has been said marginal or tender floating plants like water hyacinth are more useful until the water clears.

Thanks to everyone sure I will get sorted now!