# Midday lighting break for planted tank



## goh (Jul 9, 2004)

There is an article at the dennerle website claiming that giving the planted tank lighting a midday break is "amazingly effective at combating algae". Please read the article from the below link.

http://www.dennerle.com/ENGLISCH/E_Algen/E_Algenframeset.htm

Click on "TROCAL Light for aquaria" and then click on "Tips on lighting on aquaria" to read the article.

This article seems to contradict with the Blackout theory for elimilating algae.

Any comments on this?


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## budak (Mar 13, 2004)

There are several different types of algae. The so-called black-out method is effective for blue-green algae (aka cyanobacteria, not algae actually), but not things like BBA, brush algae etc...

I am afraid I find Dennerle's proposed method unhelpful, even detrimental, as plants don't seem to like the disruption to their daily photosynthetic cycle much. Ergo: if the plants don't flourish (due to insufficient light/fert/Co2), what's the point?

The idea that algae declines in the presence of healthy plants seems to be more credible. This means providing ample and consistent Co2 (20mg/l or more), continuous, regular lighting cycles and a full spectrum of fert (NO3, PO4, K, Fe, micros) amidst regular water changes. There is, of course, the alternate approach of no-water change, no fert, low-to-medium light setups, which also works, but that is another (long) story.


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## plantbrain (Jan 23, 2004)

I never found much merit to the mid approach although many seem to swear by it.

If you have good CO2, NO3 etc, then it's simply not needed.
If you have weak CO2 then the break will allow more time for the CO2 to build up to solve the deficiency.

But if you did things correctly and had a control, you'll find there's little merit to the approach, unless you just want to have weak CO2 levels or some other weird notion about how to grow plants.

Give the plants what they need to grow, then there are no algae problems.
Once you figure this philosophy out, life is good.

I had a number of issues with Dennelre's site and advice on algae.
See AQ for more on that.

I know I've done more with controls than any company has to date addressing plant health and algae.

Blackout works quite well with BGA.lower light Green water issues, but as mentioned by Budak, it is ineffective for BBA etc.

But keep in mind there are *midday blackouts *and then there are *3-5 day blackouts*.
Do not confuse the two types.

I find the midday routine to be usless if all other parameters are accounted for.

These produce different results and are different in their approach.

Regards, 
Tom Barr


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## goh (Jul 9, 2004)

Thanks for the replies. 
This more or less confirm my doubt on this Dennerle article.


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## HeyPK (Jan 23, 2004)

I agree with the others. 

I took a quick look at the Dennerle article and saw a lot of statements that contradict well established knowledge about algae and higher plants. All the green algae (Chlorophyta) are very similar to members of the plant kingdom in their photosynthetic pigments and general biochemistry. In fact, at least some of the green algae are under consideration to be included in the plant kingdom. I doubt very much that a mid-day light break would adversely affect algae any more than it would the rest of the plants. 

Right at the beginning of the article, where the effects of putting a new fluorescent bulb on an established tank are discussed, I found a lot to take issue with. I especially don't believe the claim that the increased oxygen from the increased photosynthesis due to the new light would precipitate out reduced iron compounds. Virtually all iron compounds get oxidized to ferric at oxygen levels too low to support fish life. If fish were living in the tank lit by the old light, the ferrous compounds will be oxidized to ferric already. 

While it is true that a higher light level can cause plants to become iron deficient that were not at the lower level, the reason is due mostly to the fact that a slow growing plant can absorb enough iron and other nutrients to keep up with its growth rate even when nutrient levels are low. However, when the plant is fast-growing, it can develop a deficiency at low levels of nutrient availability because it now needs to absorb nutrients more rapidly to keep up with its growth rate.


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