# how long to have light on in tanks



## Johnnyfishtanks (Apr 21, 2010)

so i have 180 gallon . three metal halides 175w each how long should i have lighting . every few days i have algae on my glass and my gravel turns brownish . i have 8 hours a day right now
can i do less lighting like 7 our 6 hours ?


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## Johnnyfishtanks (Apr 21, 2010)

anybody ?............................


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## t-bore (Apr 21, 2010)

I have the lights on my 125 on at 7am and off at 9pm. Some algae on the few rocks in the tank and i run the algae magnet over the glass once a month or so, but nothing out of control. My 50 gal on the other hand seems to be a loosing battle with algae and the lights are only on from 1pm to 9pm. I am almost going to take it down because its frustrating me!


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## eternity302 (Apr 22, 2010)

Out of my knowledege, could be 6-10 hours! Ranging on what kinda plants you have as well! Some plants need more,s ome plants need less, and it judges by your light as well, if it's too strong or too light~ But all trial and error! =) hope someone that's smarter can help ya~


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## keitarosan (Apr 21, 2010)

i have mine for 8 hrs. 36" T5HO on 33g heavily planted tank.


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## Captured Moments (Apr 22, 2010)

Johnnyfishtanks said:


> so i have 180 gallon . three metal halides 175w each how long should i have lighting . every few days i have algae on my glass and my gravel turns brownish . i have 8 hours a day right now
> can i do less lighting like 7 our 6 hours ?


Is that a planted tank? I have no experience with metal halides but it seems to me that you have too much light given your particular plant biomass, Co2 level, nutrient level perhaps. As a general rule, I like to say 8-10 hrs is a good average for photo period but yeah you can try reducing the period to 6/7 hrs. Somehow I don't believe the algae you have has anything to do with the duration of your lights. It could be more to do with the intensity of it and how you don't have the required balance for the light intensity level.


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## scherzo (Apr 24, 2010)

We need a bit more information.

How long has the tank been running?
What is your plant mass?
Are you running CO2? (you should be with that kind of lighting)
Are you dosing ferts?

All of these in the correct balance (including lighting intensity) can keep algae at bay. Brownish algae usually means it is a newish tank but can also mean something else is going weird.


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## snow (Apr 21, 2010)

My 135g tank with just rock and fish in it I don't leave it on for more than 5hrs a day.
My salt tank will run double that a day.


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## neven (May 15, 2010)

can you raise your lighting a bit to see if it helps?


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