Light exposure

[Alec18]

Hello so I have a question about changing light exposures on my fish tank. So I have a 20 gallon tank with various fish from black mollies to albino African clawed frogs. I don't have a hood light I'm just using a lamp my grandma gave me that is fluorescent. I leave it off in the mornings and turn on for a little at night. And I turn it off when I sleep. But when I turn it on again all my fish are either laying on the bottom, moving slowly, or lose a lot of color. For example my tiger barb has a black strip along his face and when I turn the lamp off for awhile at night and turn it on again his head is completely white but like five minutes later it's all back again. So I'm just wondering if all this is normal or not.
Thank you
-Alec

 

[fort384]

Sounds a bit abnormal, though may not be a cause for alarm.

How many fish are in the tank, are there live plants, and what are your readings on ammonia, nitrite, and nitrate? What is the temp of the tank? Any discoloration in the gills of the fish (red or inflamed) or any labored gill movements?

 

[Alec18]

Everything is perfect and the temp is 78 F with 10 inhabitants including the frogs and shrimp. But I read they do that to conserve energy.