Just introduced only 3 black clown to my tank?

[Don S]

Earlier yesterday morning I introduced the black clownfish to my 50 gal. 50 lb. live rock aquarium.

Throughout the day I watched the clowns every now and then, noticed their activities/behavior.

In the beginning, they seemed a bit shy of swimming around the tank, and instead, stayed on the left side against the wall, danced together for quite a long time.

Slowly slowly, inch by inch, they danced from top to bottom of the tank, and meanwhile, I fed them multiple times in small amounts throughout the day.

I'm curious to find answers to couple of questions as I observed their activities.

1) How come they are lined up together and constantly moving (or "dancing") while they are together?

Is it that they are just enjoying and having fun?

2) Also, there is cave-like rock housing in which they didn't enter until half of the day was gone.

I'm wondering why they took so long in deciding to enter their cave? They now mostly stay just in there and come outside from time to time. But what do they do in there anyway?

3) I took 10-15 gallon of water to do water change to lower salinity levels, but one interesting I noticed while doing this is that this absence of 10-15 gal. water caused the filters outake tube/hose to create lots and lots of small bubbles since out take tube was above the tank water level now, so the water flow into the tank made bubbles.

Interestingly enough, the clowns were viewing the mini bubbles as if they were some type of food which they tried to eat. Any thoughts why they were trying to eat the bubbles?

4) I turned off the light fixture on top of the tank just to see what happens.

One or two of them seemed to start freaking out due to absence of light. Why is that anyone knows?

And is it okay for me leave the lights off at night time? Don't they need to sleep?