Acipenser ruthenus?
I couldn't spot a label, so I may be wrong about the species - all the sturgeons look quite similar. Please comment if you think I'm wrong.
@gentle lemur I think this is might actually be a Siberian sturgeon, Acipenser baerii but pretty sure they did have both species at one point. Sterlets are usually slimmer bodied with a longer snout, prominent white tips to the pectoral fins and scutes whereas this fish is quite uniform in colour. Though I'd also be happy to be proven wrong
There was a Siberian sturgeon in the next tank, which was labelled, but I couldn't get a decent photo. But it was rather larger than these sturgeons, so you may be right.
