Welcome to the site!
I've shot my friends 5d2 and it is unbelievably better than my camera lol. You much have spotless glass, everytime I try to shoot the light through the glass, all I see is streaks and spots and any glass imperfections.
Thank you Scars
I do keep the glass clean, but the way that I get such clarity is from the twin flashes on 21" flex arms, this alows me to flood the tank with light from the sides or top, overcoming the flaws…Most of the time