Fish Pond how to return with sour the algae? i have a big fish pond and surrounded by it i have...

i have a big fish pond and surrounded by it i have 6 kois, the sea gets thoroughly green from the algae which make it concrete to see the fish even with the pond lighting, i used algae controls but still equal someone told me to paint the pond with a black paint so the algae don't grow surrounded by it. what kind of paint should i use my pond is made of concert .
Answers:    EDITED:PLEASE READ
what you enjoy described is pea soup algae PLEASE for they health of your KOI read the links below this type of algae cuts stale the oxygen supply.
OXYGEN is a key constituent with koi unless you hold a good filtration system and aerator you can't use singular the barley (which is excellent) you must circulate . **** YES ****A UV filter
will positively REMOVE (split pea) this type of algae. HOW DO I KNOW THIS? I lost 3 fish in sooner or later and immediately know what happened. I WAS idle and didn't change the lights contained by the filter soon enough. I would enjoy lost all of them but I begin pumping fresh water contained by and pumping out the old at like time.
I then took out the rest of the fish and completely empty the pond replacing the lights in the filter and tally fresh water.
The UV hurricane lantern does not add chemicals.

http://www.richkoi.com/kpnet/algae.htm
Murky Pondwater? You Need a Combo UV and Biofilter
http://www.garden-ponds-algae.com/
So Koi call for a lot of oxygen, almost as much as we do when resting.
http://www.coloradokoi.com/koi_oxygen.ht...
http://www.koigarden.com/cat3.html

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Depending on the pond size select a UV light will remove the green.
I use 24 watts surrounded by my pond but it is small only 2000 gallons at present time. Also using an aerator will prevent it. Algae doesn't approaching lots of oxygen but koi REQUIRE a lot .
The aerator will back provide what your fish are in short supply of right in a minute. This is my hobby so I've researched everything possible.
Here are some suggestions and links for research on what you need and costs.
http://www.azponds.com/
Laguna Aeration Kit
This is apposite for the size and price
2 for 34.95 each or 39.95 for one free shipping
http://www.azponds.com/air_pumps.htm
Changing your plant soil can assistance prevent the algae as well
http://www.schultz.com/ProductCategories...
Click on photo to see what size you would stipulation it's a combination of UV and BIO filter.
http://www.drsfostersmith.com/product/Na...
Use oxygenator plants as well to create a fluent filter system as well.
Good Luck!
PS I prefer NOT using chemicals surrounded by my pond The link below is exceptional for a massive knowledge of garden ponds and the fish . They will convey you free a monthly news message, with loads of information. http://www.pondmarket.com/about_us.htm
try chitchat to a fish store for one. Try alge eaters, there pretty harty and will amaze you. Again, talk to your fish store.