It might be a stupid question on my part, but I was wondering if maybe fish find a quiet spot in their natural environment, out of the current, when they want to rest at night.
Here is the article where I read about shutting off the filter: http://aquaticfrogs.tripod.com/id1.html
I copied and pasted the quote where it is mentioned:
"I would also overfilter when it comes to the care of these frogs, it really helps with the water quality. For example, i use a Whisper powerfilter ment for a 70 gallon tank to filter my 40 gallon tank. I also suggest shutting off the filters at night. It gives them some peace and quiet and they do become very alive and active at night. I have been doing this for years and it has not made my water dirty or anything."
I have read this a few different places, when I was researching this topic.