This tank holds an amazing collection of sturgeon, from the mundane to the insanely rare.
From top to bottom -
Russian sturgeon just at the top (Acipenser gueldenstaedtii), note short snout and yellow scutes
Sterlet facing left (A. ruthenus), dark with white edges to fins and white lateral scutes forming a line
Starry sturgeon just below (A. stellatus), long slim snout and very prominent scutes on a dark background
Another Russian I think
Amur sturgeon (A. schrenckii) in the middle facing right, long and slender but with more prominent scutes than a Siberian
A pair of sterlet to the far left
And finally at the bottom a Fringebarbel sturgeon (A. nudiventris) with the very prominent shoulder rise and scutes behind.