This is basically what the Great Lakes Aquarium was like 20 years ago. At the time the shipwrecks gallery was a temporary Lake Victoria exhibit with cichlids, Nile Perch, lungfish, crocodile, etc., the two larger Isle Royale tanks were divided into then/now, with "then" featuring only native species and "now" including the introduced salmonids, and there was an invasive species area with lampreys, rusty crayfish, etc. I think average patrons found the local focus boring and repetitive with most larger tanks anchored by some sort of trout or salmon, so attendance dropped and they eventually had to diversify to survive. It's similar to what took place at Adventure Aquarium, which started out as the "New Jersey State Aquarium" with only native species.