Fish don't need light on their tanks. Room light is sufficient for them to see and do their day to day things. Plants need light and we need light to see our fish. So the convicts will be fine without a light on their tank
Exactly, there are cloudy days in nature and for some seasons it can be dark and gloomy for what seems like weeks on end (we western new yorkers wouldn't know anything about that.... ) So the fish won't get worried or frek out. As long as there is ambient light in the room, they will prob go on like nothing is wrong