The little tank with the algae has the purple starfish, shrimp and Cowfish in it. It's only about 900 x 300 x 300mm in size.
If you want to go around the complex more than once, don't go on the 'Ride the Dive' until last, as the exit for this is the gift shop and I don't think you can get back in from there.
Also if you buy something from the gift shop, the back of your entry ticket should have a 10% discount voucher on it - we didn't notice this until after we left!
See how you go at photographing the lion fish and the big Wrasse, I didn't have much luck with either!