Black water (algae)

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So I did install the UV light and as promised, it cleared the green algae in just 2 days!
Everything seemed to be going fine for a while, but then ths weird black algay grew almost overnight first on the waterfall stones, then on the walls of the entire pond, making the water look dark...it is now still clear (I can see the bottom and all the fish just fine), but the walls are covered with this black algae, I've never seen before!(a bit smelly too) and the whole pond looks so dark, I worry that this new algae can be harmfull for my fish!
I do not want to add chemicals, but I need to know: are my fish ok in this condition??

pond size: 3000gl
fish: 12 (10 koi, 2 shubunkin) 15" average
Ammonia: 0
Nitrite: 0
Phosphate: 0
PH: 8.5 to 9 (always been high)
 
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I personally wouldn't worry. I get a black, gel like, algae on the edge of my water fall sometimes, and I just brush it off. If it were me, I'd lighten feedings a bit , to see if your fish will nibble on the black algae.
 

sissy

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that is the good stuff that means your pond is balanced and the fish love it .If you have a clean liner it means you are doing something wrong .The stuff on the rocks helps clarify your water
 
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Tula, Sissy, I'm not talking about the common film that develops on stones, this algae is not slimy nor stringy like the usual stuff, this looks like a thick layer of black hard grass about 3" to 4" long! it comes off very easy, just by running my hand across, leaving the stone perfectly clean....but grows right back in just a day or 2
I wanted to take a pic but all it shows is black algae, I have to try taking a closeup maybe later after work
 
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I'll be interested to see a picture. Honestly, I rarely worry about algae ....but you could increase aeration and water movement, if it's getting out of hand.
 
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I'll be interested to see a picture. Honestly, I rarely worry about algae ....but you could increase aeration and water movement, if it's getting out of hand.
I have: 2 individual waterfalls (22" each) , 2 air pumps and 4 heavy duty pond air stones, I would not know what else to add

Yes, please post a photo.
I will try later!
...I need to clarify something, when I said: "this algae looks like grass 3" to 4" long" I forgot to say that it is not standing up like grass, it is laying down
 

sissy

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sounds like string algae and comes from to many nutrients in the water .You may need to test your water and remove some of it by hand
 
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Algae will only grow when the conditions are correct for it to grow it needs
  1. Nitrates and to a lesser extent nitrites,
  2. Phosphates,
  3. Light,
  4. Reasonable temperature.
A UV light stuns the Algae, causing it to fall out of suspension so your filters can remove it or it falls to the bottom and is consumed by beneficial bacteria. If your water still has the Nitrates and Phosphates in it, with no algae to consume it, something else will.
If I were you I'd try to get as much of that black "algea" out as possible, and make sure there isn't a layer of mulm (dead algae, bacteria, fish waste and decaying plant material) on the bottom. If the black is "a bit smelly" as in earthy or musty, your probably not in too bad of shape, if it's "a bit smelly" as in sulphury, rotten or putrid I'd be much more worried and aggressive.
At any rate do some water changes, what ever it is will probably have some significant BOD (Biological Oxygen Demand) issues.

"pond size: 3000gl, fish: 12 (10 koi, 2 shubunkin) 15" average" seems like a lot of fish for 3,000 gallons too, 2 Koi and 10 shubies would seem a better fit to me. At that load your going to have to manage it quite intensely to keep problems at bay.
 
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