I have 4 tin foil and 4 koi, size around 2 inches, 7 tiger barbs ~1inch.
In 30 gn tank, when the lights are on, they are mostly at bottom. When I turn the lights off, I can see them moving all around.
At feeding time, When I turn off the filter, I usually do that when I feed them, they immediately come to surface, become super active (all of them) even before I lift up the lid. That's the best time to watch them. Finishing the food within 2 mins.
Are they afraid of lights? Or filter (it's a regular top filter).