# Low light tank, how many hours?



## jmsaltfish797 (Oct 27, 2012)

eleven hours is bordering on being to long of a photo period. normally you want to run your light for about 8-9 hours, even with low light. much more then that and you will start to have problems with algae.


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## xmas_one (Feb 5, 2010)

That's kinda lengthy, even low tech I like to limit photoperiods to ~8 hours max.


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## EvilFish (Oct 15, 2013)

So, from 11am to the 19pm? But most of the day my tank will be too dark... 
8h is really ok with 0,7w/gallon?

And how about fishes? They will like 8h daylight? 

Thanks


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## Raymond S. (Dec 29, 2012)

Depends on which fish. Most will like it more. Actually fish need no light other than indirect sunlight as in...as long as there is
a window that is open(no curtains covering it or venetian blinds either) so you can see good enough to do whatever in there
without turning on a light...that's good enough for them. Plants of course need more than that.
I once had my lights on a complicated timer system where one bulb came on from 8A till 6PM. And the other bulb came on from
about 11A to 3PM. to simulate the mid day high amount of light. All it did was cause mega algae.
I now have two tenG tanks, one/w T8(two strip light fixtures..one front of tank and the other back of tank). Actually that tank looks
better that the one/w the T5(yea on a tenG) and both sort of mid level tech. Excel/ferts, but as prescribed by the manufacturer
and liquid not dry. The one/w the T5's get them more regular. I say better than, but as far as viewing light levels and as much
of the tank/w good levels of light as in hardly any shadows anywhere, but no large plants yet.
The one/w the T8's gets 9.5 hrs and the one/w the T5's gets 8 hrs. Both tanks have just been re-planted so not at their best
for me to say look at my gallery but 8 hrs is good for both fish and plants for two bulb systems or LED lights and 9-10 for one
bulb systems. Google each fish to see if it likes low light. You can provide shade for those which like low lights.
And putting a piece of fiberglass screen between the bulb and tank reduces light by up to 40% so that is an option also for
a portion of one end for example. This link shows light needs for some plants.
http://www.aqua-fish.net/index.php?cur_lang=2&count=no&secured=&section=6


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## EvilFish (Oct 15, 2013)

Thanks

Fishes:
Angelfish
Corydoras sterbai
Harle. Raspbora
Platy
Brazilian Ram


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## The Big Buddha (Jul 30, 2012)

I split my lighting period 4 on 2 off 4 on.
Welcome fellow montrealer.


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## EvilFish (Oct 15, 2013)

Thanks

Split the lighting won't stress the fishes?


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## EvilFish (Oct 15, 2013)

Can I add something like 3w submerged lighting only to see the fishes?


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## jmsaltfish797 (Oct 27, 2012)

if your running low light you shouldnt have any problems with the fish being stressed. i run at 8 flat on my tank with no probs. if viewing the fish is the issue, set the light to come on later in the day. that way you can enjoy the tank without going crazy with the light cycle.


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## lochaber (Jan 23, 2012)

EvilFish said:


> Thanks
> 
> Split the lighting won't stress the fishes?


I've heard about split photoperiods for quite some time (I think I remember reading about it back in the early 90's...), and I never ran into any verifiable claims that it was harmful/stressful. Some people claim it mimics mid-day storm/cloudcover, but I haven't heard any verification about that either.

Diana Walstad, in her book "Ecology of the Planted Aquarium" (which I highly recommend to anyone/everyone), has a brief mention of split photoperiod helping with CO2 in lowtech tanks. 

small chart on p 179 for those with access to the book.

She's measured the CO2 levels every 2 hours in a tank lit from 7AM to 9PM, and one lit from 7AM-12PM, and from 4PM-9PM. she measured the CO2 levels at about 7AM, 9AMish, 12PM, 4PM, and 8PM (not stated, I'm guessing based on the chart).

both tanks seem to go from 8-10 mg/l of CO2 in the beginning, down to about 2-4 mg/l CO2 by noon. the continuously lit tank reaches near 0 mg/l by the 4PM measurement, and remains there at the 8PM measurement, while the tank with the 'siesta'/split photo-period returns to ~8-9 mg/l CO2, and ends at ~6 mg/l CO2 for the final measurement. 

Granted, it's just two tanks, but I don't think the general trend would change much with more tanks/repetitions (the numbers would probably get a bit more precise though.

also, I hope my attempt at conveying her simple graph via text was understandable to someone...


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## anastasisariel (Oct 4, 2009)

When I had my first high tech setup my biggest mistake was giving the tank waaay too many hours of light. 

Also going by watts per gallon is also a HUGE mistake if you are using T5 or LED lighting...

I'd start at 8 hours and slowly work my way down while observing your plants.


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## Christophe (Oct 23, 2013)

I'm running a split photoperiod on a moderately-planted 40g breeder, about 4.5 hours each lighted period, 2.5 hours off. Testing nitrate & phosphate levels twice a week, I've noticed that the plants consume more nutrients using a split photoperiod than they do on a single period.

It doesn't bother the fish at all, and the downtime happens when I'm at work anyway -- I get more lighted time when I'm actually home to see it.


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## The Dude (Feb 8, 2011)

For me it depends on a number of factors to include plant mass, C02, fert usage, etc. my tanks are all medium light and either DIY CO2 and / or Metricide. They get 10 - 11 hours and then an hour or so of moonlight. I don't have any algae problems and routinely feed my Oto's, Nerites, and Amano's so they don't starve. I've worked up to this and many of my bulbs are in need of replacement


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## EvilFish (Oct 15, 2013)

I have a T8 20w 6700k bulb over 29g.
T8 need to be ON 8-9h too?


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## freak (Oct 15, 2013)

I do a split schedule with my low light plants. I do 6 to 8 in the mornings and 3 to 9 in the evenings.


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