Red Tailed Black Shark

[esce]

I've had my red tailed shark for months now, but just now as I was cleaning out the tank, something happened.
I transferred him into clean water to begin with, as I usually do. He immediately freaked out, and jumped from the bowl. I retrieved him carefully and replaced him into the clean water, he then stopped moving. Paniced, I tipped the bowl back in the tank. He stayed at the bottom, seemingly unable to swim but still breathing. After a while, he stopped moving completely.
I'm extremely upset, and confused over what happened. Is he unconscious? dead? why?

 

[WILDER]

You should never move fish to maintain the tank. It's to stressful.
Also clean water the water stats can be different sending them into shock.
Was was the ph of the fresh water to tank ph water & temp.

How many gallons or litres is main tank.
How many fish and which type.
Water stats in ammonia, nitrite, nitrate, and ph.

Add some stress coat to main tank.