# Green Algae



## Larry Hudson (Sep 28, 2008)

I have a 48" x20"x12" fish tank containing six goldfish measuring about 7 inches each. There are two catfish type algae eaters about 7 or 8 inches long. The tank has been in place for about 12 years.

I use a Fluval 4 internal filter and employ an air curtain.

I do not heat the tank. Water changes, involving approximately two thirds of the water, are made on a monthly basis. The filter is cleaned bi-weekly.

Except for becoming slightly cloudy towards the end of the monthly cycle, the tank has appeared fairly clear and sparkling until the past couple of months when it began to seriously cloud with a greenish hue. I tried several water changes in rapid succession, together with replacing the filter medium.

The only thing I can come up with as a possible cause is green algae. I cannot see any solid evidence of this like a stringy or leafy substance, just the green discoloration of the water.

The fish do not appear to have been affected, but the appearance of the tank is not a pretty sight.

I wonder if anyone else has experienced a similar problem and if they discovered a remedy. Any assistance would be greatly appreciated


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## Shattered (Feb 13, 2008)

It sounds like you have "Green Water", you could probably try a blackout. 

The first step would be to try and find the cause. I think more frequent water changes of 25% once a week, would help out. That is once the green water has been fixed.


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## Riceburner (Mar 14, 2008)

+1 ...you would be better off going with less volume and more frequent water changes. Say 25% weekly.


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## ameekplec. (May 1, 2008)

Like was said before, go smaller and more frequent. 

You've also got way to much fish for a tank that size. The goldfish and plecos both poduce a lot of waste, so I'd imagine a lot of it isn't getting cleand up.

Do you siphon the gravel when you do water changes?

Also, you could look into a UV sterilizer for your tank, which will rid it of green water.


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## Larry Hudson (Sep 28, 2008)

ameekplec. said:


> Like was said before, go smaller and more frequent.
> 
> You've also got way to much fish for a tank that size. The goldfish and plecos both poduce a lot of waste, so I'd imagine a lot of it isn't getting cleand up.
> 
> ...


Thanks for the advice. Will try more frequent/less volume water changes.

The fish have been in the tank for many years. They reached maturity and stopped growing several years ago, but the green problem did not occur until very recently. The 50 gallon tank does not appear to be overcrowded.

I did turn off the canopy light for several days to see if it would help, but it did not.
The tank is located in my living room, it is completely dark only at night, Not sure how to effect a blackout.

Am not familiar with the UV sterilizer. If it is an expensive piece of equipment, I doubt I could afford it. If it is affordable, would love to know what it is and where it can be obtained.


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## Darkblade48 (Jan 28, 2008)

I won't comment too much on your fish choice/stocking options; needless to say, what's been said so far is true (regarding the fish).

As for the cheapest option (a blackout) to eliminate the green water, you have to ensure that no light gets into the tank. Do a semi-large water change before doing a blackout to eliminate some of the green algae. Turn off your canopy light, and cover your entire aquarium with heavy blankets/black garbage bags or the like. Ensure that no light is getting through, and be patient. It takes at least 3 days for the algae to die. During this time, there is no need to feed your fish (you can feed them a little more a few days prior to the blackout). Peeking will only let in light, causing the green algae problem to linger, so be patient and restrain from peeking (as hard as it might seem). After the blackout period, do another semi-large partial water change, as any dead/dying green algae can cause ammonia spikes.

Alternatively, you could purchase a UV light, as has been mentioned. I've never bought one, but they do work in killing off green algae. I think you're typically looking at < $100 for a UV sterilizer, but I'm not sure of their pricing (though I'm pretty sure you can get cheaper ones from the sales thread, etc).


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## Larry Hudson (Sep 28, 2008)

Darkblade48 said:


> I won't comment too much on your fish choice/stocking options; needless to say, what's been said so far is true (regarding the fish).
> 
> Alternatively, you could purchase a UV light, as has been mentioned. I've never bought one, but they do work in killing off green algae. I think you're typically looking at < $100 for a UV sterilizer, but I'm not sure of their pricing (though I'm pretty sure you can get cheaper ones from the sales thread, etc).


Thank you for your assistance, it is greatly appreciated.

Will follow your advice on the water change and blackout. I will keep you posted.

The fish stocking worries me as I have become attached to the critters.

I rechecked them carefully this morning. (My original size estimate was off the top of my head) A careful estimate shows the red and silver "goldfish"
are each about 7 inches long; The redcap is around 5 inches. the other three
appear to be about 4 inches. One algae eater is about seven inches, the other is slightly smaller, say six inches.

I believe the tank hold 50 US gallons of water, it is 48 inches long, 20 inches high and 12 inches wide.

During the Summer we experienced a problem with the canopy (it cracked and the glass was discolored) We purchased a new one. The light tube in the old one gave a bluish light. The new one gives a greenish light. However the new canopy and light were in place for about 3 months before the algae problem manifested itself.


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## Larry Hudson (Sep 28, 2008)

. Turn off your canopy light, and cover your entire aquarium with heavy blankets/black garbage bags or the like. Ensure that no light is getting through, and be patient. 

The tank is now under blackout. We removed 15, two gallon buckets of water.
Replaced the water with fresh (treated) water. I had a roll of black landscape fabric left over from the garden. Cut to size and folded four times, it is a perfect lightweight blackout material. 

Will leave the blackout in place until Friday and then see what happens.

Thanks for your assistance.


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## Larry Hudson (Sep 28, 2008)

Three days blackout. Water change prior to and after blackout, but no real improvement to the green water problem


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## ameekplec. (May 1, 2008)

Do you ever clean the substrate? Sorry if you've said so or not earlier. It's the only thing I can think of in an old tank to suddenly manifest algae problems.

If not, give the substrate a good cleaning, and suck up all the gunk accumulated under there. The clean out the filter, and then do a black out, ensuring that there is no light. If 3 days didn't do it, do it for 5. Your fish won't care much, and you have no other plants in there, so it won't matter if it's dark for a few days.

As for aUV unit, usually new one for a 55g tank will run you at least $120, probably more cause you're on the rock. You might be able to purchase a cheaper one online, but not sure of that. As for used, you might be able to have one locally or shipped to you. GL with the green water.


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## Larry Hudson (Sep 28, 2008)

Thanks for your response Ameekplec. Yes I gave the substrate a good cleaning, but the water I retrieved was green rather than dirty. We did another water change this morning (six buckets 15 gal) There seems to be a slight improvement. We have left the light off, but have not yet done a second blackout. We thought we would feed the fish and give them a 48 hour break before imposing the 5 day blackout.

I have been trying to get a handle on the uv sterilizer. I have found a couple of Ontario based Aquarium supply dealers who offer them, but I can't seem to find a good illustration or reference as to what they actually do. I take it that some sort of light is employed to sterilize the water, but am concerned over the possibility it also destroy the bacterial balance of the tank.
Will keep looking.


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## Shattered (Feb 13, 2008)

Here is a great article on the basics of UV sterilizers.

Basically, your aquarium water passes thru the unit. The microorganisms are bombarded by UV light which destroys them. In your case the algea spores would be killed, but would still remain in the water so water changes will then rid you of them.

It will only kill free floating micro-organisms, so the beneficial bacteria that adheres to rocks and the filter will not be harmed.


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## ameekplec. (May 1, 2008)

Basically what Shattered said. The UV destroys/damages DNA and other organelles (parts) in cells and kills bacteria and other organisms, effectively sterilizing the water.

And yes, it does not affect bacteria in the filter.

They usually work by having water pass through a glass or plastic tube around a UV bulb, thus bombarding the water (and anything in it) with UV light. There are different sizes/wattages of bulbs and their usage depends on the flow rate through the UV chamber.

If you're looking for a good one, check out Katalyst's ad. A great UV unit for an unbeatable price, and is the right size for your tank too:
http://gtaaquaria.com/forum/showthread.php?t=5004
Maybe she can work out shipping for you.


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## Cory (May 2, 2008)

Another alternative is to try adding some live plants to your tank. They will compete with the algae for nutrients and photosynthesize more quickly than algae will which can kill of the green water. That said, the high stocking level of the tank will produce lots of excess nutrients so it will be difficult to manage nonetheless. 

When you clean your filter media how is it done? Do you clean it under tap water or with used tank water? If you're using tap water, that could also be your problem as you'll be neutralizing beneficial bacteria that breaks down ammonia in your water. If the ammonia is in excess, the algae will capitalize on any ammonium particles that form and use it as fertilizer to grow.


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## ameekplec. (May 1, 2008)

Cory said:


> Another alternative is to try adding some live plants to your tank. They will compete with the algae for nutrients and photosynthesize more quickly than algae will which can kill of the green water. That said, the high stocking level of the tank will produce lots of excess nutrients so it will be difficult to manage nonetheless.


Goldfish will eat any and pretty much all plants you put in there. Also, you'd have to really fill the tank (a big one) to have the desired effect, and that would cost a hell of a lot more than the UV sterilizer. But a good long term alternative in smaller tanks.


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## Cory (May 2, 2008)

I thought carp were insectivores, my bad !


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## ameekplec. (May 1, 2008)

haha,

Carp eat crap, and everything else. Ever smelled the flesh of one? Smells like mud.


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## Cory (May 2, 2008)

lol. I try not to make a habit of smelling my fish, that is assuming you meant living ones.. I smelled a dead koi once, it was sealed in a plastic bag but it was still god awful and when my friend walked away with the bag.. know what.. I could STILL smell it in the air  . I can only imagine what it's like when storms or other disasters cause tons of fish to wash up on shore for people who live in those areas. Poor souls! Ok, enough hi-jacking of this thread for now lol.. back to green water!


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## ameekplec. (May 1, 2008)

Cory said:


> lol. I try not to make a habit of smelling my fish, that is assuming you meant living ones..


Nope...worked in a fish market for a while. They smell and apparently taste like mud too.


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