Green Water

D

DaShark

AC Members
Sep 13, 2004
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I have a 20 gal. fishtank that has been set up for almost a year. For the past month, though, the water has changed to a green tint. I have researced a solution for this on the internet, and it said to do water change and add a algae killer, I used liquid called Algae Destroyer. The water changes and the Algae Destroyer have made no difference in the color of the water. I only have about seven small fish in the tank, and none of them seem to be bothered by the green algae water.

I anybody knows a soloution to this problem it would be greatly appreciated.
 
Green water is caused by a bloom of free floating algae in the water. The only real cure is to attack the causes: too much light and/or too many nutrients in the water column.

What can you tell us about the amount of light, natural and otherwise, the tank receives each day.

Nutrients in the water are the other cause. These include nitrates, phosphates and other organic compounds. What additives do you use? How frequently do you change water, and in what percentages relative to the tank's volume?

Jim
 
Do you have a planted tank or not?

If you do not have a planted tank then perform a 'Black Out'. Turn off the lights on the tank, cover it with a blanket or such, and leave it in the dark for a week or two. There won't be a problem with you occasionally uncovering it to feed the fish for a few minutes every day or every other day.

If it is planted then perform a 'Siesta' every day. Do this by blocking off all light for a couple of hours in the middle of the lighting period each day.

Algae is a more primitive organism than plants. When light is turned on or off, it takes far longer for the algae to start or stop photosynthesising than plants.

In addition to this, algae is not good at storing reserves, like plants do. So they need a fairly regular supply of light to produce available food.

They are weak. So starve the little boogers.

And don't add any more of the Algae Killer. Throw that in the garbage.
 
Fully agreed that the algea killer is a bad thing. Large volume water changes, combined with a blackout. The blackout will kill the algea, the water changes will work on the cause which is more important. Watchers methods are a little different than mine, but hey that's OK. I black the tank out for 4-5 days with or without plants. plants will easily get through that time without light, and algea cannot as said. Don't feed during that time, and keep up on the water changes. Green water won't hurt your fish, but it will not go away without the blackout or other drastic measures. at some point it will be as thick as pea soup an drive yu totally nuts though.
dave
 
I have struggled with green water several times in the past. Typically the cause is high nitrate levels. Like others have said, large, frequent water changes should help with these levels.

If you want a sure-fire solution, you can look into Diatom filters. Obviously these aren't the cheapest answer, but they're guaranteed to clean the algae out. I used one to clear my 90g cichlid tank of an algae bloom I got while cycling, and it did an amazing job. As with any other solution, though, you have to attack the root of the problem at some point (the high nutrient levels), or it will just come back.

The other bonus to Diatom filters is that you can run them once or twice a month for an hour or two, and you'll have crystal clear water.

Good luck!

-sj
 
I'm going to try to blackout out my fishtank and do the water changes, do you think two water changes in a week would be enough, or should I do three?
 
It depends. What percent volume are you changing each time? How heavily stocked is your tank? How heavily do you feed?

In general, I would think that 2 50% water changes per week should be plenty. But if you're overfeeding, over stocked, then you may need to do more.

Get a NO3 test kit (optionally, also get a PO4 test kit). When I was having algae problems in my 10g learning experience/fish killer tank, I realized after testing the water that both my NO3 and PO4 readings we off the charts. You don't necessarily need both, if you bring the NO3 down and feed lightly in a properly stocked tank, PO4 should come down too.

Yes, a diatom filter would probably clear your water right up, so would a UV sterilizer. But for me, there are other things I'd rather spend a few hundred dollars on than something that gets used a couple times a month to do what regular tank maintenance and proper fish husbandry does for free.
 
as said if the volume is good, 2 would be plenty, if you have time for more do them. if not that's fine. For me when I use the blackouts, it's essentially a resetting period for my tank. get rid of all excess waste, kill all algea (doesn't work for BBA) and remove it all from the tank. so I reccomend high volume frequent water changes. in reality, 2 a week should keep the tank clean, deal with extra waste, and the blackout will kill of the green water.
dave
 
You really need to consider what goes into the tank, too. For example, many of the pH regulators (e.g., Proper pH) are loaded with phosphates and create conditions ideal for an algae bloom. Excessive feeding and/or insufficient waste export (via water changes and/or gravel cleaning) also contribute. Control the amount of nutrients in the water column, and you can almost always control the algae breakout.

Diatom filters and UV units can be used in situations that are resistant to simpler methods, but diatom filters and UV units are really just treating the symptoms, not the cause.

HTH,
Jim
 
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