# Lighting Schedule - blackout period



## AlexTal (Mar 23, 2006)

In Peter Hiscock's Encyclopedia of Aquarium Plants, it's said that some people use a "siesta" time or a "blackout" period of 1 to 2 hours in the middle of the day as a way to fight off algae. Does anyone use this method? Would it actually hinder the plants from photosynthesizing as well? The schedule would be something like: lights on at 6:30 AM, lights off at 12:30 PM, lights on at 2:30 PM, lights off at 8:30 PM. The result would be 12 hours of light in total, just broken up. Thoughts?


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## Zapins (Jul 28, 2004)

I don't think it would be a good idea to stop and start like that.

I have heard that plants take a few hours to get warmed up and start photosynthesizing at efficient levels. If you stop and start like that, then they have much less time to gather energy.

Why not just reduce your lighting hours to 8-10 hours. I noticed the largest benefit when I reduced the lighting time from 10-11 (4wpg) to about 8 hours (at 2wpg).


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## AlexTal (Mar 23, 2006)

I haven't had any algae problems, yet ...

I'll just keep a normal schedule then. I was wondering if anyone had any experience with this. Thanks!


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## John N. (Dec 11, 2005)

If we think about how the sun is in nature. The sun doesn't stop shining at noon for us or the plants. So it's not something we want to mimic. 

Like Zapins said, plants actually do need a few hours to being their photosythesis and continuous light thereafter to reach the full potential. Cutting them off could lead to weaken plants, and the ultimate result would be algae taking a foothold over the less than perfect plants, since algae needs less of everything to get established.

Continuous lights: even if it's the 1 bulb in the morning, 2 bulbs in the noon, and 1 bulb on at night. 

So to answer your question yes I think it will hinder photosythesis, and will also result in the promotion of algae growth.

-John N.


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## BJRuttenberg (Sep 25, 2005)

This may by unfounded but I heard that algae actually takes a longer time than plants to begin photosynthesizing light and the break, in a sense, inhibits algae growth to a degree...just what i've heard


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## AlexTal (Mar 23, 2006)

BJRuttenberg said:


> This may by unfounded but I heard that algae actually takes a longer time than plants to begin photosynthesizing light and the break, in a sense, inhibits algae growth to a degree...just what i've heard


It might not be, however. Peter Hiscock made this claim in his book as the reason for a "siesta" period. He said something along the lines of plants can almost start photosynthesis immediately, but algae can not. I'm sure he claims references for his information, I should take a look and see where he got this idea.


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## snowy (Jun 6, 2006)

I'd be interested to know more about that as I've also heard the exact opposite - that algae can start photosynthesizing far sooner than higher plants. I'll have to dig through my books to see if I can find where I read it.

To me this does make sense if you consider than many stem plants take a short while to open up in the morning and close in preperation of lights out in the evening.


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## AlexTal (Mar 23, 2006)

Hiscock says, "Plants are able to regulate the rate of photosynthesis relatively easily, and quickly respond to changes in light conditions. In other words, they do not take long to warm up and start photosynthesizing once there is sufficient light. However, algae are not as biologically advanced as plants and need a long and relatively uninterrupted period of light to function properly. It is possible to combat algae in the aquarium by controlling the intensity and period of lighting in the aquarium and creating a "siesta" period. This is a period of darkness that interrupts the normal day/night light cycle in the aquarium. If the aquarium receives 5-6 hours of lighting followed by 2-3 hours of darkness and then another 5-6 hours of light, the plants will be relatively unaffected and receive enough light throughout the day, but algae growth rates will be significantly reduced and may even start to die back."


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## Smokin_Cache (May 22, 2006)

I can add that in my 125 I have had a pretty bad battle with hair algae. I read the comments for the tank of the month and decided to put a break in my lighting. After two weeks I have noticed a reduction in algae and no difference in the plants.


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## ens124 (May 26, 2005)

I practice the siesta in my 84gal aquarium and the plants are flourishing with minimal algae.

From the Dennerle guide:
Aquarium plants need a day/night rhythm. Experience has shown that a daylight period of 10-12 hours give the best growth rate.
A "siesta" has proved successful:
In the morning 4-5 hours of lighting. Then a dark phase of 2-4 hours. Then lighting again for another 4-7 hours. During the dark phase the aquarium should not be in complete darkness (diffused light from a window or from a lamp).
Contrary to popular opinion, we have not noted any negative effects on either fish or plants, presumably because strong reductions in light intensity, e.g. due to noonday thunderstorms, are quite common in the tropics.
Algae evidently do not enjoy such "siesta". Whether this so because the "primitive" algae are less adaptable than the "modern" aquarium plants or whether an improvement in the oxidation/reduction balance is the main issue has not yet been resolved. Against algae the "siesta" has proved amazingly effective.

Peter Yang


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## joephys (May 9, 2006)

I have tried it, I didn't have any algae when I did it, but I don't have any algae now either. I don't think it really makes a difference. The plants grew fine when I did it.


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## Laith (Sep 4, 2004)

Yes, Dennerle has been recommending this for years.

Several years ago when I briefly tried the Dennerle line of plant products I also tried this siesta break in lighting.

I never noticed a difference in algae presence or growth.

When I learned to concentrate on getting good healthy growth from the plants instead of trying to constantly manage algae, my algae issues were reduced considerably.


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## redstrat (Apr 3, 2006)

I have to agree with you there Laith, as far as photo period is concerned though I have found something interesting in my own experience. I can't say its right or wrong but its just something I have observed in my own set up. Photoperiod control is probably one of the most important things next to CO2 in higher light tanks. I used to run a 12hour photo period with 3.5wpg in my 75gallon tank with little CO2 and greenwater went rampant. I then cut the intensity of the lighting down to 1.7wpg in the same setup and added CO2, did a little fert balancing and the GW slowly went away for a couple weeks. Keep in mind I fought many other algae types during this whole GW adventure but the GW was without a doubt the toughest. When the GW returned again, I thought i needed more CO2 so I fixed that, no improvment other than better plant growth. I then decided maybe the plants aren't getting the light they need to outcompete the GW so I added a 3 hour 3.5wpg burst in the middle of the day, the plants grew a little better but no real change to the gw. This went on for weeks, I thought I was going to have to buy a diatom filter or UV because I just couldn't kick the GW. I have since decided to do something a little more drastic, I cut my photoperiod down to about 9hrs a day with the full 3.5wpg again and guess what happened, keeping everythign else the same, plant growth greatly improved, the gw has vanashed, as well as any other algae in the tank, and I have noticed a greater demand on ferts. It seems to me that maybe plants prefer an 8-10 hour solid intense photoperiod, anything longer and the plants start to slow down, regardless of CO2 levels or ferts. I'm sure my results probably wouldn't be as great with even an hour break in the photoperiod as everything seems to benefit from the long dark period almost as much as the bright light period.


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## teacherthomas (Jul 14, 2006)

I believ eby watching the plant you will realize they only want about 8~10 hours of light. The leaves will begin to close on my lotus plant when I reach 7 + hours of light at 3.2 wpg, as do the leaves on other plants. So I reduce the light to 8 hours with a 2 hour break inbetween and the plant growth is still fine. I think the lighting demands depends on your tank. Watch the plants in the morning, at mid day and the evening and you will notice their reaction to the light, from that you can judge how much of a lighting peroid you need.


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## acuajuan (Jan 30, 2006)

I'm not so experience in this things but I was using a siesta break in photoperiod and it worked well, near no algae at all in the tank (also following the seachem schedule for fertilizing) I changed recently to a continuos 12 H of light and it seems to me that I have more green spot algae now than before, may be because other reasons but....

I hope it helps...


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## fsnow55 (Jul 30, 2006)

I tried this, it seems* to work i.e. reduced the amount of bba in my low tech 100g to almost non-existent (remnant on java ferns). Substrate looks so clean that I noticed some gravel colors that I didn't before. 


* unfortunately, I added a number of other changes 
as well, so I don't have a good control experiment:

1. upgraded the 4xT12 daylights with 4xT8 daylight (both philips daylights) probably got an extra bulb (in terms of lumens) with the increased efficiency.

2. fertilome hydroponics Fe fertilizer (small quantity enough to cloud water; which cleared up next day).

3. 1-2 h siesta in 12 hour break.


Other contributing factors:
1. Plants grew faster (with better light?) and outcompeted bba?

2. Since the overall aquarium is brighter, the algae eating fishes (golden loaches, cherry barbs) are now grazing in the formerly darker part of the tank. Cherry barbs are also observed nipping bba (as before) although I don't think they cleaned up enough to make an impact?



I don't care what really happens, bba is gone  but I might not be lucky next time it occurs, so a really conclusive finding would be great.


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## bpimm (Jun 12, 2006)

John N. said:


> If we think about how the sun is in nature. The sun doesn't stop shining at noon for us or the plants. So it's not something we want to mimic.
> -John N.


John, if we think about everything we do with our aquariums we probably don't mimic nature all that often. IE. 20 PPM nitrates, where does that happen in nature? usually a superfund site.       

I use the noon blackout to achieve my goal. having the tanks on when I get up and have breakfast and have them on in the evening while I relax before going to bed.


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## peewee790 (May 26, 2007)

Great info! I've been using giving my plants and fish a 2 hour siesta in my 20gal ,3.6wpg, co2 injected tank. So far I've had great plant growth and very little algae. 
My lo-fi 10 gal tank has a 10 hour block... I have more algae there, probably for many reasons.


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## Newt (Apr 1, 2004)

I had a nitrate crash which started BBA so I quickly pruned affected plants and tried the siesta period (I also read about it in Hiscock's book). I had no harmful effects on the plants and the BBA died off. There are other methods to deal but algae and siesta is one of them. I do not use it any more but would not hesitate to again in order to control outbreaks. I also used Flourish Excel.

Algae is a primative life form and takes longer to 'gear up' photosynthesis and plants are able to turn on and off very quivkly. John N., ever hear of clouds and shadows?


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## John N. (Dec 11, 2005)

bpimm said:


> John, if we think about everything we do with our aquariums we probably don't mimic nature all that often. IE. 20 PPM nitrates, where does that happen in nature? usually a superfund site.


Ya, you're right. Our aquariums are not very 'natural' like, and probably very far from it. Natural waterways, lakes, etc. have algae and near constant waterchanges afterall.

I wouldn't say clouds or shadows would be enough to limit light like shutting off our aquarium lights. UV light does come down still. But I think it could be a combination of things i.e. clouds/shadows, and the constant changing turbidity of water ways that may effect how algae grows in nature.

-John N.


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## Newt (Apr 1, 2004)

'cept plants don't utilize UV.

My Rotala indica begins its night time curl up (where the leaf tips at the top of each stem fold in for the night) shortly after the CF's go out and just the dusk light is lit. So I think photosynthesis is affected by the amount of light.


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## gacp (Sep 11, 2006)

In the tropics, there is very often a daily early afternoon shower, from the convection of all the water vapor evaporated during the morning. About 12:00 to 15:00, I'd say. It gets quite dark.


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