# Lighting: Intensity vs Duration?



## klibs (May 1, 2014)

It's not necessarily as easy as 'one or the other'. Generally speaking if you can run high light without algae issues then go for it. 

If you are running into algae then yes - you may have too much light. Two ways to combat too much light in a day are to reduce photoperiod and reduce intensity.

It's really up to you. Higher light makes things more difficult but if the environment is right then it results in the best plant growth / results. IMO reducing light is 'better' but this is just my opinion. If your setup can't handle the amount of light you are giving it then doing it for a shorter amount of time just reduces how long you can look at your tank. Lowering light intensity is usually the first thing I do when I run into problems.

In the end you need your plants to be able to use up all the light you're throwing at them in a day. To do this they will need ample ferts / CO2 (if you have it), and plant mass. I don't think your light setup is very strong so it might be worth looking at other variables to figure out how to enable your tank to handle that light in the first place.


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## exv152 (Jun 8, 2009)

I would do one thing at a time, increase intensity but keep the same photoperiod, and base your next decision on observation.


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## anfield (Dec 1, 2013)

Well my initial observation after two days of more light was the start of minor hair algae. I have five amanos that I have seen actively feeding on it so might not be a problem.

I want plants to have "bushier" growth as opposed to being tall and skinny as they are now. For that reason I'm thinking I will try to keep the light at max intensity but reduce photoperiod and see if I cant monitor the other parameters ie Nitrate and phosphate. Tell me if I'm completely on the wrong track here.......

Also added capful of flourish once a week and a capful of flourish trace every other week. Might need to increase this dosage.


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## klibs (May 1, 2014)

Again, high light is only the way to go if you can manage it. If your tank is off balance and you are growing hair algae all over the place then I would not keep the light level at max.

Your real issue may be with ferts / CO2

What is your plant mass like? Is it heavily planted?
What is your fert schedule? Do you use CO2?


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## anfield (Dec 1, 2013)

Not the best pic but this is an older picture and it has filled in more now. The cabomba and Ludwigia are much taller now. I swear the cabomba has visible daily growth. Have to trim it every two weeks. I add excel 5ml daily. API leaf zone and Flourish excel (once capful each) once per week. Also root tabs every 2-3 months. Substrate is Eco-complete. Finally flourish trace every 3 weeks. No CO2.

Rest is fish poop. Nitrates usually 10-20ppm


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## klibs (May 1, 2014)

Did you just start getting this algae now or has this always been an issue?

I don't see how you would just get algae out of nowhere with an established tank like that. Did you change anything?

Some suggestions:

You need to dose the water column more IMO. Dosing every few weeks means your plants are almost always deficient.

Make sure they have all the nutrients they need so that light is the limiting factor. you are probably deficient in multiple areas. I always recommend dry ferts over liquid ferts. They are way cheaper in the long run. I am not sure what Leaf Zone has in it but i am guessing that it is not getting it done.

you may have too much light anyways but I think dosing a proper fert line will help out so you can cross that off the list of problems.
Still I don't see how this would just magically appear... usually an established tank like that will not run into problems unless something changes.r


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## FatherLandDescendant (Jul 24, 2014)

Instead of of intensity why not increase durration?


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## anfield (Dec 1, 2013)

Sorry if I wasn't clear. 3-4 days ago I realized that I was not running either of my lights at full intensity. So I cranked it up. Two days later, I start to see little bit of hair algae. I want to keep the high lights because it might keep my plants from being tall and skinny and make them rather more bushy. So Im thinking I might reduce duration instead to compensate for increased lighting.

I do add N, P and K weekly along with flourish and trace elements. API leaf zone has K and iron. 

In any case, I am just going to keep the lights at max intensity, reduce photoperiod to 6h and see what happens. Thanks.


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## burr740 (Feb 19, 2014)

Once a week Excel isnt doing much of anything. It's only active for 12-24 hours, so it needs to be dosed daily. I would start that immediately. It will help your plants and also it acts as an algaecide itself.

Aside from that, you took a tank that sounds like it was balanced (light, ferts, co2) and increased the light, without increasing the other two. Therein lies the algae problem. Starting daily Excel will up the co2 part, plus the algaecide factor. That may be all you need. Since you are registering nitrates, there's a good chance you still have enough nutrients. Not necessarily of course, but it's a good sign. I would still cut back on the lighting, as mentioned, until the algae gets sorted out. Then you can see if daily Excel will allow you to increase the amount of light.


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## mags8679 (May 7, 2014)

is a low-tech tank, no C02 but dosing Excel, I do 6 hrs a day 2.5 to 3.5 watts per gallon, my tanks are all low-tech and heavily planted and have no algae and good grow on my plants.


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## anfield (Dec 1, 2013)

lol I wish folks would read the previous posts. I dose 5 ml excel daily. The ferts are once a week. In any case, thanks for responses. I think it will just have to be trial and error.


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## burr740 (Feb 19, 2014)

anfield said:


> lol I wish folks would read the previous posts. I dose 5 ml excel daily. The ferts are once a week. In any case, thanks for responses. I think it will just have to be trial and error.


Hah, my bad. The last post made it sound like you did it weekly w/the other ferts. The advice still stands though. You increased the lighting w/o increasing ferts or co2. So bump the Excel up. I did about 3.5x daily dose in my 75 for 6 months with great results. You could go 7.5ml for maybe a week then 10, etc.


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## anfield (Dec 1, 2013)

Thanks. I might try that approach. I do have some amano shrimp. I thought too much excel was bad for shrimp?


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## anfield (Dec 1, 2013)

Burr just looked up your tank. Quite impressive esp with just excel. Nice colors even before CO2. Well done. Hope I can get close


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## burr740 (Feb 19, 2014)

Thanks for the compliment.  I need to get around to posting some updates. Your tank looks really nice too, I meant to say that in a previous post. Im not really sure about the shrimp thing.


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## Hoppy (Dec 24, 2005)

Intensity and light duration are not interchangeable. Light intensity determines how fast the plants grow, assuming they have non-limiting concentrations of all of the needed nutrients. Light duration determines what portion of the day the plants spend growing, except that some (probably not all) plants are genetically programmed to grow for some maximum portion of the day only - some of them close up their leaves after that time has elapsed.

Also, there is a minimum light intensity for every plant that is necessary or no growth will occur, no matter how long the light is on. Intensity and duration are just two different parameters.


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