I don't know how many aquariums does Italy have, but I just found out about this on 
In the Nuoro province.
It's called "Acquario di Cala Gonone" and it's kinda great
I don't think it's as big as the one in Genova, which is very famous in the world so it has to rise to some expectations, but I think Cala Gonone is worth a visit if you're visiting Nuoro
They are opened from 10:00 a.m. to 18:00 p.m. (or until 20:00 p.m. in August) and the cost for 1 ticket is 10€ for adults, 6€ for kids and 7,50€ for the elderly and students.
In the Nuoro province. It's called "Acquario di Cala Gonone" and it's kinda great
I don't think it's as big as the one in Genova, which is very famous in the world so it has to rise to some expectations, but I think Cala Gonone is worth a visit if you're visiting Nuoro
They are opened from 10:00 a.m. to 18:00 p.m. (or until 20:00 p.m. in August) and the cost for 1 ticket is 10€ for adults, 6€ for kids and 7,50€ for the elderly and students.
But, of course, there are more things to be seen, not only the aquarium, there's the biosphere and other stuff to see, very interesting