algae in a 172g koi tank

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Ananda

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Feb 15, 2002
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My cousin has a 172g bowfront tank with about a dozen koi of various types. The smallest is about 4" and the largest is about 12". There are also a couple of pl*cos in the tank, and he has some big pieces of driftwood. He has algae constantly -- the free-floating kind that makes the water look cloudy. He has two big Eheim filters (the 2229 wet/dry and the 2028, I think), a Magnum 350, and a dual bio-wheel. His nitrates are near-zero.

My guess is that his phosphates are high; I'm going to run a test for him as soon as I find my phosphate kit.

If it isn't the phosphates, what else might cause this kind of constant algae situation?

Next, what do you suggest to control the algae?

I'll point him at Phosguard if it's phosphates, and RO/DI or Kati/Ani if we've got phosphates in the source water.

Something that worked for a while was one of those square barley straw holders, but the fish tore it apart. Has anyone tried reinforcing one of those? I'm thinking of using monofilament line to attach plastic canvas to the sides.
 
I've used the barley straw with success, if you can find a way to secure and anchor it. My bigger question would be - if the algae is free-floating, why not get a fine enough filter to pull it out? A diatom filter would do the trick, but there are also products that cause the algae to clump together so as to be more easily removed by traditional filters. A UV sterilizer would do the trick too - a very small unit did a wonderful job on my 300 gallon pond.

As for the cause, I'm clueless. Certainly the algae is living on something. Is the tank exposed to too much light, natural or bulb?? If phosphates are a problem, more frequent water changes should correct it, as I don't know of any municipal water that carries more than 0.45 ppm phosphate.

HTH
judy
 
After my 75 gallon shubunkin tank got to be about 14 months old it developed the green soupy water. I tried Phos Zorb to lower phosphates, but even the micron filter on my HOT magnum couldn't keep it clear. Then I tried replacing the old fluorescent tubes, since older tubes shift to a wavelength that algae like. After changing to new Ultra Daylight tubes the water started to clear up and is now glass clear. Four new 48-inch tubes came to about $20 at Wal*Mart. Worth a try.
 
Don't rule out nitrates (or phosphates) as potential contributors to your friends algae bloom. These could be consumed very efficiently by algae resulting in low or zero test results. I would expect at least a moderate amount of nitrates in a tank with a dozen koi...even a 172G tank.

The suggestion to check on lighting (both type and duration) was a good one. Check into your friends maintenance practices as far as water changes and cleaning gravel.
 
> if the algae is free-floating, why not get a fine enough filter to pull it out?

That would be the Magnum 350. It's on continuous "water polishing" mode.

> A UV sterilizer would do the trick too - a very small unit did a wonderful job on my 300 gallon pond.

Interesting. What size (wattage) sterilizer did you use?

> Ultra Daylight tubes
What color temp are those -- 6500K?

...working on finding the phosphate test kit...we just moved and some of my fish stuff is still in boxes.
 
I don't know why the Mag-350 with the micron filter isn't grabbing it - other than the fact that I've (personally) never thought much of that particular filter. Have you tried adding some DE to it?

My sterilizer's got a 20 watt bulb - and that handled 300 gallons under direct sunlight on summer days. So maybe even an 8 watt unit would do it. I would certainly try the clumping agents first though, and save the money. Very rarely should you have to use UV indoors to kill algae. I would go first with other's suggestions on lighting changes (the barley straw is cheap enough too). How many hours of the day are the lights on?

good luck
judy
 
DOH! Forgot to ask about lighting. But given the layout of the place, I bet it gets some direct sunlight.

The Mag 350 *is* grabbing the stuff; it just gets "full" extremely quickly.

The phosphates are *definitely* playing a part. I used a Fastest kit and ended up with a reading of 4.0.

Crud. I just checked the phosphates of our source water here: 0.8 straight from the tap. (We live about a mile away from them, so it's the same water.)

On the bright side, I don't think I'll need to supplement the phosphate in my planted tanks. :rolleyes:

Aside from buying stock in Seachem for all the Phosguard he'd go through, what do you suggest for long-term solutions? RO/DI, UV sterilizer, both?
 
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I have used the barley straw in my koi pond. I put it in a lingerie wash bag. It has a zippered top and a real fine mesh. It free floats and my koi leave it alone. I'm not sure if it would work in a tank, but it's always worth a try.

I was told that my algae problem was due to overfeeding the Koi. I cut back drastically on feedings, added the barley bag, and the algae went away. It was crystal clear all summer (and it was a hot one)

Good luck with whatever you try!

DrD
 
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