Direct sunlight, good or bad?

manowar669

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Sep 11, 2004
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I was wondering if direct sunlight on the aquarium was good or bad. I have a 55G FW with two 32W T8 Daylight bulbs, about 12 hours day cycle. Until recently I was way underlit, probably why Anubias were my only reliable growers. I upgraded to the above lighting, which is probably barely adequate, but I'm getting there.
 
Direct sunlight usually will cause a bout of unwanted algae. It is best just to get the lighting you need for a planted aquarium of course catering to the plants that you intend to keep.

Marinemom
 
But indirect sunlight can work. Setting up a tank across from a window and have the light coming in at an angle away from the tank may be sufficient with somne strategic planting. High light plants closer to the sun etc.
 
What sunlight is, is very tricky. I grew some plants in front of a south facing window one summer. No problems. Then in November the sun got low in the sky and the sunlight started hitting the tank. I thought at first that would be okay the days were short and all. Soon enough the water was turning green.

At certain times of year a few of my tanks get some early morning sunlight and some late afternoon sunlight. I don’t seem to have any problems with that. It is very striking to see sunlight in an aquarium

See if you can find “The Natural Aquarium” by Yoshino and Kobayashi They use sunlight in some of the tanks in that book. My local library has that book.
 
I have a tank that get filtered direct sunlight..a little green algae but not any worse than my tank with 3 wpg.

if you get a lot of light and add artificial light you may get an imbalance..
btw willow branches will fix that problem.(live cut branches will out compete the algae.)
 
Green water

Recently I just noticed that my tank water is getting green too...though from indirect sunlight...its right beside the window but I always have the blinds down...
 
in my experience, a tank in direct sunlight will become an algea farm in no time.

certainly, i have a 55 up against a wall with a window right next to it, i left the curtains up for a a few days and have green algea spots all over the tank
 
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