Originally Posted by xxabc
They see their own reflection. I think the light glares DIRECTLY off of the glass when the outside scene is dark, and acts as a mirror, even if slightly. Which worries me, because at night, sometimes the family will turn off the living room lights and disregard the bettas. It happens hours on ends while I do homework sometimes too.
Ahhh I HATE it when that happens... my betta bit his tail until I got a timer. Now the lights are only on during daylight.
With reference to treating sick fish, I find keeping the tank light off (daylight should not be an huge issue) a VERY big help with treatment. Not only does it allow the fish to rest and sleep more, but some meds such as levimasole are light sensitive and won't work for crap while you're blasting your T5HOs over a high tech tank.
Also when fish are injured... keeping the light off is again a big help for traumatized fish. And even when acclimating new fish it sort of gives them "less to deal with".
All in all with many animals I find that 'mood lighting' is a big big BIG help with stress of any sort. The less visual stimulation they are processing and the more they're resting/sleeping, the more energy goes into fighting bugs and recouperating.