I put my 90 gal
fresh at eye level for my 18 month old. He has loved watching the fish all along. I give him the floating pellet container, closed, and tell him to "give them a little shake" he loves it.
Now the big thing is he likes when I put him up on a stool so he can watch "Dory" in teh salt water tank.
If I had to do it over, instead of the variety of fish in the fresh, I would have gotten a huge amount of schooling fish. He loves going to the fish store and loves the fish taht come to the front for him. Nothing better than the happy squeals of a young 'un