I have two Painted Portside Fish that both have the "Near any Aquarium Ruins (decorations)" Buzz Bonus. It's X'd out for both fish, despite there being no Aquarium Ruins in the tank. I'm guessing this is a bug as I have a Flying Fish with the same Buzz Bonus in the same tank and it's working correctly (green check).

I attached screenshots showing one of the Painted Portside Fish with missing Buzz Bonus (in the tank without Aquarium Ruins item) and one showing the Flying Fish in the same tank. 

Note: I have tried putting both Painted Portside Fish into my inventory and then back into the tank and I have also exited the museum and loaded back in - the issue still persists. Also, there are no Aquarium Ruin items in any of the other tanks in the museum. In another tank, a Hermit Turtle has the same Buzz Bonus that is working correctly.