# Optimal hours of light



## Fishbarrie (Feb 13, 2015)

I have a 90gal high tech planted tank with medium to high light requirements. I currently run a two bulb T5HO which covers the total length of the glass top tank. Tank is 48in wide and 24 tall with no floating plants. How many hours per day should this light be left on for optimal growth and color? Thanks.


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## klibs (May 1, 2014)

Depends on a ton of factors but generally 8 hours is about average for how long people leave their lights on. Some people do 5, some people do as much as 12. I would say 8 is 'standard'


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## BBradbury (Nov 8, 2010)

Hello Fish...

Most the plants you get for your aquarium are tropical and used to long hours of daylight. My tank lights are on a timer set for 12 hours on and 12 off. I use T8 four bulb shop lighting for my larger tanks. You can go as long as 14 hours, but that would likely be the longest period.

B


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## sevendust111 (Jul 15, 2014)

I am pretty sure the standard for high tech high light is 8 hours a day

Bump:


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## dukydaf (Dec 27, 2004)

Aquatic plants would often be shadowed by the canopy or other plants for at least part of the day. In nature the leaves are also covered by biofilm, fine particles and algae.The high intensity, vertical light that we provide should not be compared with natural conditions. 

You have to decide/discover what is optimal for your aquarium. As other suggested aim for about 8h. I would suggest start with 6 if the aquarium is new.

Look at the plants, some plants like Althernathera close their leaves when they want to go to sleep. If you go alot over the 'optimal' duration you might get algae.


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## al4n (Nov 18, 2008)

Photosynthesis period is different to all tanks as there are alot of different variables between setups. If the tank is new, i suggest starting at 5-6hrs and gradually adding more hours as week goes and monitor your algae growth. For example with my tank if i go beyond 8hrs algae starts to grow, so i leave it around 7-8hrs.

Sent from my SM-N910G using Tapatalk


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## Daisy Mae (Jun 21, 2015)

dukydaf said:


> You have to decide/discover what is optimal for your aquarium. As other suggested aim for about 8h. I would suggest start with 6 if the aquarium is new.
> 
> Look at the plants, some plants like Althernathera close their leaves when they want to go to sleep. If you go alot over the 'optimal' duration you might get algae.


Agree with above. 

I tend to start with 6, then go upwards from there. My tanks with brighter light usually do not need to budge from this. I have not exceeded 8 hours in any of my tanks. 

If you have ever bought Tropica plants, their packaging also suggests 6 hours to start with. I'm going to guess they know what they're talking about :nerd:

Are you in Barrie? I lived in Ontario for six years, in-laws are in the
area.


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## bsherwood (Nov 22, 2007)

I was 10-12 hours on my planted tanks. Keeping algae under control was pretty constant. I dropped back to 6 hours a couple weeks ago and I have noticed significant changes. I am going to experiment going to 7 hours and see what that does for me.....but , for me, it was clear that "less is more".


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## essabee (Oct 7, 2006)

When you talk about plants, most people think that they react to variables in a set pattern - but that is not entirely true there are various degrees in that reaction even in the usual general direction and some exceptions to the general directions may also exist. Plant evolved in competition with other plants and survived by adaptation to various niches in the environment where they could out compete their rivals. So each plant specie is slightly different from the other species and even within the specie there might even be slighter differences between individuals. So optimal for one may not be so for another.

In natural habitats light varies in spectrum, duration, intensity not only over stretches of area but also with the time of the day as dukydaf pointed out above. The spectrum varies with time of the day - longer wave-lengths being higher in the early and later parts of the day. The spectrum of light of the stretches lighted by indirect light have lesser amounts of the reds. Intensities vary to the maximum when the sun is at the zenith etc etc

When it comes to your individual tank - you create a niche with with your light pattern, flow and nutrient regime. By varying the light alone you are changing just one part of the environmental niche; this presupposes the others were invariable - that's not true - so finding the optimal duration would not depend on the light itself.

Optimal for the hobbyist would be the sweet spot where all the variables are set in a way creating a tank environment which would cause the set of plants in the tank to grow well and out-compete the algae.


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## Fishbarrie (Feb 13, 2015)

Daisy Mae. Yes living in Barrie.. but it feels like Victoria weather. Will be 10-12C tomorrow and sunny!! Going to take the Harley out for its last ride this year 
Thanks for the advice.


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## Daisy Mae (Jun 21, 2015)

Ha ha, enjoy the ride tomorrow! It's warmer there than over here. 

Hubby's already there in Severn Bridge helping out his sister with renos. I'm sticking around for a bit until the kids finish school, then we will fly out for Christmas. We will see if there's snow.


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