Nah, I wouldn't get that. It would probably be fun for some people, but you can just as easily make your own goldfish toys
And the tunnel is a bit too small, you'd have to make a few DIY tunnels anyway for the goldfish to get used to the idea of swimming through a dark passage like that
I think I told some techniques and items you need in this thread already: (Link is not visible to guests. Please register to view.