It's those adorable "I'm a big kid now" moments that really make a parent smile. From switching to underpants from diapers to replacing the crib with a bed we live for that look of joy on their little faces. Though it may be tempting to buy your small one an aquarium, heaters and all of the decoration just to see that look again, it's important to ask yourself first whether the child is ready for such a responsibility, because it's not just your child's happiness that's at stake, but that of a living, breathing, helpless fish as well.
Some things to look for in your child to see if he or she is ready:
Memory and Routine. Does your child have a routine that he or she is able to follow on a daily basis? For instance, can he or she remember to brush his or her teeth after meals? Or, do they remember the way to get from their home to school? If so, he or she can probably be relied upon to remember to feed a fish, especially if the fish's feeding time is linked to something in the child's personal routine, such as a meal.
Personal Responsibility. Does your child recognize his or her own belongings and want to look after them? A child who values his or her toys is much more likely to be able to recognize the value of their new pet and want to keep it safe.
If a child has started school it is generally a good indicator that he or she will be mature enough to look after an animal. Schools often use small animals such as fish or hamsters in the classroom to help teach responsibility and the same methods can be used at home. However, keep in mind that even if the pet nominally belongs to the child, it is still important for parents to supervise their care and handling.
Find more information at Is Your Child Ready for a Pet?.