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Light duration

1482 Views 9 Replies 6 Participants Last post by  Jnad

I have just started a new dirt tank with dimmensions 30cm X 30cm X 35cm. The light is a 18W PL tube.

What light time duration would you reccomend? Should i start with less hours when the tank is newly planted?

The plants is easy fast growing plants from Tropica.

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I think most people would recommend an 8 hour photo period, and the 8 hours doesn't have to be continuous either. As for how long the photo period should be when you've just set up your tank, I think I read that it's better to go with a shorter period at first and then gradually lengthen it.
I do think the light looks a little strong, is it a good idea to use the window screen on the picture?


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Looks bright already even with the window screen. You still might run into algae problems unless you does CO2.
You can use multiple layers of window screen if u need to. That does look bright.

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Start at 8 hrs. If you start to see algae reduce the lighting to say 7 hrs. If you reduce the light to 7hrs and you still see algae, you may have to add more screen. If you reduce your lighting and add screen and you still see algae, you may have to reduce your lighting with a new bulb or get a small CO2 kit.
I have two tanks, bothhave about 30cm from light bulb to sub.
Both are on 7.5 hrs per day and one is over 2 years old and the other is over 1 year old so I don't see why so many people want those long hrs of light in their tanks.
I have T8 x 2 bulbs in one of them which should be high end of low rage and T5 x 2 bulbs in the other one which is hard to detrmine the level of because some say the
brand offixture that it is has a substandard ballast supplied/w it which has less current
than normal but the thread on here about lighting with PAR states that at 30 cm it
has 100 PAR for that brand of fixture. The light in this tank is defused partially by
the use of Giant Duckweed which is reduced each week and has about a 15% coverage at the beginning of that time. So just how could you determine PAR in this tank ?
But I would say it to be safe to say it is at 65-80 PAR so I guess it to be at med/high
range of the med light level. It is only fair to say this tank has hair algae in it but it
is intentional and the amount is regulated b the use of the GDW and Excel @ 2x the normal doses.
When plants are jst getting established, unless you have very low lights it may be
wise to use less hrs till they get growing well. I would not start with more than 7.
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Thanks for your replies.

I will start carefully with 6 hours, and increase to 8-10 hours after some weeks depending on algae growth.

Looks bright already even with the window screen. You still might run into algae problems unless you does CO2.

If you don't mind my chiming in, the light looks too bright to me too.

I would use non-metallic windowscreen (very thin) which takes the light down 40% I think, or find a way to raise the light six inches or so (If you're not using CO2) or switch to a lower wattage bulb. I've had good results with raising my Compact Fluorescent lights 4-6 inches (and switching to a dirt substrate recently).
Hmmm, it is not possible to use a lower wattage bulb, i am using an external ballast that is rated just for two sizes, 24 and 18W. All the plants in the tank is fast growing plants, i will watch for algae and hope for the fast growing plants to outcompete any algae.

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