When my CK was bout 8inches it always used to hide whenever the light was on. I went on a 3 week holiday nd forgot 2 turn off the lights so the lights were on all day for a 3 week period. When i got back it no longer hid, but swam around with the lights on
. Maybe because i left the lights on 24-7 in got aclimitised to swimming around in lit conditions and no longer was frightened by a bright tank..