I would say to go during the day. I did and there were no line ups. The fish were incredible to see and you could touch some too!
I went with my adult children and we all felt like it was worth the money and time.
It is about a 2 hour tour and you should wear good shoes to do such an activity.
Benches are there in certain spaces for people who like to sit and observe the different fish. I went in 2016 of January it was great!