OK, yes, so fish do disappear, and or hide all the time, but it can be amazing how a big, thin fish, like an angel, or silver dollar, can disappear... my only angel fish or silver dollars right now, are larger mature fish, and there has been times, I've spent 15-20 minutes looking for them... these particular fish are all the more dominant in their tanks, and don't try to hide, but even being large, and not appearing to "try" to be hiding, can be hard to see... big as life from the side, but so thin, they can be difficult to see from the front or back...