Diversity - the quality or state of having many different forms, types, ideas, etc.
This is a great place to take kids because it shows them how diverse the ecosystems and animals living in the world are. The ocean makes up 70% of the World and just about every animal depends on these vast bodies of water for survival. It's important to not only inform but show our children that we are not the only habitants in the world and that it is important to protect other animals that cannot protect themselves.
You can purchase tickets to The Florida Aquarium directly for about $25 per adult and $20 per child that's age 3 years old and up.
If you want to take on seeing everything that Tampa has to offer such as Busch Gardens, Clearwater Marine Aquarium, MOSI (Museum of Science & Industry), and Lowry Park Zoo in addition to the Florida Aquarium I would definitely recommend purchasing Tampa's City Pass which allows you to visit all of these locations and skip lines for $99 per adult and $89 per child. You'll be looking at a 50% savings in comparison to regular admissions pricing for all locations.
Now some public schools in Hillsborough county also offer free Florida Aquarium tickets for students and their families (which is how I got to enjoy the aquarium). I would advise contacting your child's school and asking about free or promotional events for students.