I have had my ten gallon tank set up for over a year. I really don't remember when I did it, but it has been awhile, and was set up using the gunk from my little 2.5 gallon. So it isn't really a new tank. I originally had five white clouds in there, three females, two males. I have never had these fish before, but I would say they acted normal. They'd swim all over the tank.
I would guess about five or six months ago, they started hiding. They almost never come out to the front of the tank anymore. I have plastic plants, rocks stacked to make a couple caves, and had a plastic plant with java moss on it (which has temporarily been moved to a new home). During this time, they have spawned. I have five that have survived to be big enough to not fit in mouths or get sucked up by the filter. I had not intended to breed them, so after the first surprise batch of fry, I have not tried to save any. Also, I have lost two of the females during the last six months or so.
Anyway, it occurred to me this morning that about five or six months ago, I also got a modem sitting under my computer, which is directly across from the tank. It has about six little green lights that shine towards the tank. Since fish like a period of darkness during the night, I was wondering if these could be bothering the fish, since it isn't completely dark? Stressing them out? Nothing else has changed here. I also do not have a background on the tank, so the white wall shows behind it.
I intend to get a background in a few days, when I make the weekly trip across town to the lfs to pick up crickets for my toad. Even if it isn't bothering the fish, it should look nicer. I also will try draping my fish tank towel over my computer chair, and block the light to the tank tonight, to see if it helps. Why it took me so many months to think of this, I don't know.
I don't have to be awake for two more hours... Maybe I can go back to bed now...