Blue planet is rubbish!
They have fish as well as a planetarium and other cool things at the world museum in Liverpool and it's free :)
I was a bit disappointed with blue planet, I thought it would be bigger, especially for the price. BUT, my daughter loves aquariums so I’d go again.
I vouch for world museum. Its free. It'll last longer than either of these you have suggested.
Don’t bother with the Cheshire oaks one. My little girl loves fish so I thought I’d take her there on my birthday… She was excited the first couple of big tanks, then wanted to just wander round and didn’t really look much. In the tunnel she was more interested in the moving floor than the sharks and rays etc above her 😅😅 we spent 2 hours there and that was a stretch x
Neither tbh, they’re both so expensive for the hour or so you spend there x