Hello,
No idea how I spotted this but it is rather strange. Check the picture below:
I have circled in red a hole in the coral, I don;t know what your meant to see in this hole but the hole changes colour as different fish swim over it. Just watch that area and wait for adifferent fish to swim over it. As the whole reappear from behind the fish the hole has a colour the same as the last fish that swam infront of it!
Weird but I guess we all want this aquarium free of bugs before it's is released!
Thanks
Regards,
Neil