It's amazing how much conversation can take place between a two-year old and an aquarium. Let the kids name the fish. Have discussions and ask questions like, what color is that fish? What are the fish doing today? Count the fish. Just be careful with counting. If one of the fish has decided to eat some of its tank mates that could turn into a different type of learning experience altogether. This doesn't necessarily have to be a bad thing; you just have to be prepared for it. After all, kids do have to learn about the cycle of life and death somehow. It would certainly be a lot easier to cope with the death of goldfish as a child's first loss, rather than a human family member.
In these times of having five hundred plus cable channels and excessive video games, an aquarium can be a refreshing touch to a home. The next time you sit down for a family dinner; try looking at the aquarium instead of the television. You never know, it may just start an actual conversation.