Dear RTR sir, with all due respect. I entirely understand the massive difference of what we see from the outside and what the fish could see from the inside could or would be entirely different. But though I have not tried it myself nor with the periscope, I still feel that they would see at least a faint reflection of themself from the glass. Especially when the background is darker or when the exterior light is dimmer than the tank. Similar to when we are walking in the mall, we would still see ourself against the shop glass.. Quite clearly at times..
I am not a Troll, I am just pissed..!