It is quite new - approx 18 months old. Worth a visit if you are in Malta anyway, but I wouldn't make the trip just for this.
@DavidBrown Yes...mostly Mediterranean fish and inverts. No birds or mammals. There is now a small reptile/ amphibian section.
I've been twice, and for me, the highlight was the innovative building. It's nothing special if you have visited lots of aquariums, but worth a visit if you are in Malta. Great cafe too.