# How much light is too much?



## madison_cichlid_mom (Aug 13, 2017)

I have a Marineland double bright LED strip over my 75 gal Tang tank. It is perched about 8 inches above the glass top. Over time the tank side of the glass top gets an algae scum on it (it doesn't touch the water) and I have to razor blade it off (plus the built up hard water deposits). I just did that and now I noticed my tangs (Cyps, Eretmodus, Calvuses and Synodonts) are in their caves more often and not free swimming. I guess I noticed this before but never paid much attention.

I experimented by putting a longitudinally folded dark blue towel on the glass top, effectively blocking a lot of the light and making the tank much darker with the diffused light. Then I noticed everyone was out and about.

I don't have a planted tank (although I might consider some java moss and anubias to suck up extra nitrates) so am I safe to use a towel or some other method to block the light? It never occurred to me that it might be annoying the fish.


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## tanker3 (May 18, 2015)

Your lights are on too long. I just turn my lights on for a few hours when I get home or feed them. Less then 2 hours usually, at times maybe 3.


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## caldwelldaniel26 (Jun 11, 2017)

I'm assuming it's not possible to adjust the white intensity on that particular model? If not, you should consider something with a remote that you can adjust the lighting. I use fluval aquasky on mine with the white intensity turned way down and the blue all the way up, really brings out the color of the fish.


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## madison_cichlid_mom (Aug 13, 2017)

tanker3 said:


> Your lights are on too long. I just turn my lights on for a few hours when I get home or feed them. Less then 2 hours usually, at times maybe 3.


The brightness of the lights is the issue, not the time they are on.


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## madison_cichlid_mom (Aug 13, 2017)

caldwelldaniel26 said:


> I'm assuming it's not possible to adjust the white intensity on that particular model? If not, you should consider something with a remote that you can adjust the lighting. I use fluval aquasky on mine with the white intensity turned way down and the blue all the way up, really brings out the color of the fish.


I wonder if I can put this on a dimmer specifically made for LEDs?


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## caldwelldaniel26 (Jun 11, 2017)

madison_cichlid_mom said:


> tanker3 said:
> 
> 
> > Your lights are on too long. I just turn my lights on for a few hours when I get home or feed them. Less then 2 hours usually, at times maybe 3.
> ...


I agree, my fish don't like the lights very bright either. I get way more activity out of them when it's dim. It actually may be possible to put a dimmer but some LED lights don't work with them.


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## madison_cichlid_mom (Aug 13, 2017)

Yes, I read up about that, I think the blue towel is the best option. Maybe leave a foot open at one end and put the plants there...


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## caldwelldaniel26 (Jun 11, 2017)

Sounds like a plan, ghetto but it works lol. Definitely a lot cheaper than buying new lights! Maybe you could tint the glass lids instead of using a towel perhaps


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## DJRansome (Oct 29, 2005)

If you have multiple bulbs...remove one or more.

As an aside...the fish will be healthier if the lights are off at night and I would not have lights on more than 8 hours daily...even with plants.


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## madison_cichlid_mom (Aug 13, 2017)

No, this is a specialized LED strip light. And it is off at night, after 8 hours on.


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## awanderingmoose (Aug 11, 2016)

FWIW, I too run a Marineland double bright, the 2' strip over a 40. Have no problems. Sure, the fish are often hiding, but that's their natural behavior. Don't particularly notice any more algae in the tank than in any of my other tanks.


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## DJRansome (Oct 29, 2005)

And maybe it was only temporary due to the recent scraping...just reacting to the change but will adjust.


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## madison_cichlid_mom (Aug 13, 2017)

Maybe. They do come out more if the towel is on the top. I'll make a more permanent light block.


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## Mcdaphnia (Dec 16, 2003)

A more permanent setup, would be to replace the light with a shorter one that only illuminates part of the tank. I have some tanks set up like that and it creates a natural look that does affect the behavior of the fish favorably. It is easier to set up with the light just on the right or left half of the tank so mine are that way. I have plans for setting up a tank with only the center half under the light.


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## madison_cichlid_mom (Aug 13, 2017)

Or I can put the towel over one half..


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