# Do blackouts really work?



## Zapins (Jul 28, 2004)

I asked my Algae professor if a 3-4 day blackout would kill off single celled algae. He said no, it would just cause them to form spores and they would come back when conditions returned to normal.

Are blackouts actually effective?


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## Faruk Gençöz (Nov 4, 2005)

To get rid of BGA experimentally I changed the water completely 4 times within a week without touching the zone BGA appeared. It did not work. Then I darken the tank completely for five days. It was still there. Then waited two days more in complete darkness. It was still there. After the 7th day I removed the BGA mechanically and changed the water again and turned the light on. In the other morning it appeared exactly in the same zone. Then I added 6 corries to the tank. Two days later it disappeared.

So I would say there are multitude of factors that help combatting the algae. Blackout is one of them and I guess it can be a necessary but not sufficient factor to get rid of the BGA in my case.


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## Navi (Jun 24, 2005)

Blackouts are effective against BGA and green water. I don't think they have any effectiveness against other types of algae though.


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## niko (Jan 28, 2004)

Black out does get rid of some algae but that doesn't necessarily mean they die. Maintainting a planted tank means to not give a reason for the algae to grow too well.

A black out gives you an advantage but that's all.

--Nikolay


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## BryceM (Nov 6, 2005)

Maybe the main purpose is to keep the tank dark enough that you don't obsess about the algae for a few days!!!


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## Laith (Sep 4, 2004)

guaiac_boy said:


> Maybe the main purpose is to keep the tank dark enough that you don't obscess about the algae for a few days!!!


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## jerseyjay (Jan 25, 2004)

Aqua-planted setup will always have algae ! Growing algae means "healthy" tank. The secret is to keep it at bay and grow healthy plants instead of annoying algae.


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## HeyPK (Jan 23, 2004)

Bluegreen algae (cyanobacteria) protect themselves with a variety of poisonous or repellant substances. Snails eat only a little when the BGA is in light, but if it is kept in darkness for a few days, the levels of toxins drop, and the snails can start to make serious inroads. A good way of getting BGA under control is to have a bunch of ramshorn or pond snails present, remove large accumulations of BGA by hand, and then keep the tank dark or in dim light until the snails clean up the remainder. 

Many hair algae are almost impervious to blackouts. I once tried a prolonged total blackout with Oedogonium---the one that produces 0.5 centimeter fuzz all over everything---by keeping a liter container of it in a cupboard for six months. When I returned it to the light, it was still all alive, and it started growing immediately. The only effect of the 6 month blackout that I could see was that the fuzz became 1.5 centimeter long instead of 0.5 centimeter.  

If your green water is very thick, don't do a blackout without doing a major 80% to 90% water change first. The whole tank can go anaerobic when that much algae die. Start the blackout or brownout when you can still see objects through at least 15 centimeters (6 inches) of water. Just cutting back the light to 1 watt per gallon often works with green water.


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## plantbrain (Jan 23, 2004)

Zapins said:


> I asked my Algae professor if a 3-4 day blackout would kill off single celled algae. He said no, it would just cause them to form spores and they would come back when conditions returned to normal.
> 
> Are blackouts actually effective?


It will kill off the established adults, it will not kill spores that are released under stress conditions.

These spores germinate under specific environmental conditions.
For BGA, these are dirty filters /substrate etc, or low NO3.

Adding Blackout + KNO3 dosing addresses the control and long term prevention.

If you did the blackout correctly, 3 days should do it in everyu and all cases, if not, you did something wrong. Typically, not covering trhe tank so that no light at all gets in. Or did not remove as much as you could prior to the blackout.

Low light tanks can get rid of GW with blackouts but it's typically ineffective at higher light intensities.

Regards, 
Tom Barr


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## Zapins (Jul 28, 2004)

Hmm, interesting. So i will check the NO3 levels and add a bit more, then perhaps i will cut the light hours back from 10 to 8 for a week or so and possibly then do a thorough cleaning (again for the umpteenth time) with my diatom filter// 80% water change and follow it up with a blackout and then a water change and cleaning when i turn the lights on again after 3 days.

Hopefully in that way their numbers will have been reduced during this week of less lighting//more NO3 and then the water change//diatom combo should kick their asses more. Followed up by the blackout to get the adults and then the secondary water change to get the zoospores that they release during the blackout. 

By the way, does excel help these things grow? Also should i up the CO2 more? Its at 47ppm now.


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## plantbrain (Jan 23, 2004)

The mukltiple approach method works best IMO, wise choice to go after it with a number of apporaches.

These approaches will also improve plant growth as well.
You might be ablwe to knock it back without doing the 3 day blackout.

But you can soon tell either way, the plants will be nice a healthy prior though and be able to handle the blackout and bounce back nice and strong.
If that does not work, then you do the blackout and then that will take care of it along with good mainteance and dosing routines with KNO3.

Regards, 
Tom Barr

www.BarrReport.com


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## JaySilverman (Jun 19, 2005)

4 day blackout did not kill my hazy green water issue. It did knock it back a little though and I've noticed it got rid of some green spot and blue green algae. Tank is looking alot cleaner. I don't know what to do about my green haze though. Its been almost a month and ahalf and it hasn't gone away on its own.


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## plantbrain (Jan 23, 2004)

Blackouts are seldom effective for GW.
See Diatoms and UV's for that.

Regards, 
Tom Barr


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## JaySilverman (Jun 19, 2005)

Don't got money for those. I'm gonna have to wait it out. Hopefully it will go away eventually.


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## Zapins (Jul 28, 2004)

The diatoms i had a while back didnt seem to die out all that quickly, i had it for 3-4 weeks. Even with massive water changes every other day. Finally a diatom filter got rid of all the algae and once the haze had cleared much to my horror all the plants had suffered damage from having too little light for so long.


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## standoyo (Aug 25, 2005)

agree the blackouts have to be done properly with kno3 dosing to rid of bga. otherwise it will be in vain as it will come back in a week.


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## plantbrain (Jan 23, 2004)

UV's are cheap, see ebay, 30$.

Regards, 
Tom Barr


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