Originally Posted by
skate020
http:///forum/post/3174223
you turn the lights off when adding new fish so aggresive dominant fish in there dont attack them.....
you've never heard of that before?
This is not completely true.
While it's recommended that you acclimate fish with no lights, it's more than just for aggression.
New fish are extremely stressed, with the lights off they can calm down and adjust easily (or more calmly).
Here's what I have noticed from acclimating fish with lights on vs lights off:
~~When the lights are on, all your fish are out swimming freely, and quite interested in the new addition. Even if your existing fish are not aggressive, just their curiosity of the new fish can stress it out. This can cause ich, a floor surfer (jumping out of the tank) or cardiac arrest. It's like taking you to a different country where you know nothing and dumping you in the countries major city during rush hour with high blood pressure and an anxiety disorder.
~~When the lights are off, most of your fish are sleeping, or in their territory. Most won't venture out into the open water of the tank once the lights are off. You still may get the one curious fish that wants to know what that new object is in the tank, but one fish vs ten with the lights on is much easier to handle for the new addition. The biggest difference I've noticed is that with lights off and the fish going to bed, the new addition knows where everyone has already established territories and where the existing fish sleep. The new fish can acclimate to it's surroundings and learn, "Oh this rock can't be my bedroom, I guess I'll check somewhere else. Oh, this rock is okay, but that one over to the right isn't either." The new addition can easily find a peaceful, safe space to call home without being harassed and calm down before it has to deal with the pre-existing members of the tank. I have a much higher success with fish that I acclimate with lights off and I attribute the large majority of it to this reason.