Think you know a lot about those fish in your aquarium and fish in the wild? Because there are so many species of fish and their characteristics vary so widely, there’s a good chance there are a whole lot of fun facts about fish and aquarium living that you’re missing.

Consider these fun facts about fish for starters:

1. Goldfish have teeth at the back of their throats that they use to grind food.

2. Remember what you learned about Pavlov’s classical conditioning research? It seems to apply to fish too, as some can associate certain sounds with feeding time.

3. Playing dead by floating at the top of a tank can be a smart way for some fish to protect themselves.

4. Fish were here before the dinosaurs.

5. There are about 30,000 species of fish.

6. The world’s smallest fish, the Paedocypris progenetica, is less than one-third of an inch. This translucent fish looks like larva and is a member of the carp family. The second smallest is the Philippine goby, which is about as long as your pinky fingernail.

7. Although they feel pain and have instincts that protect them, we don’t know if fish have true emotion such as happiness. Many people believe that they don’t, but it’s possible that we haven’t learned to pick up on the cues that indicate their emotions. A human who is happy, for example, might smile, and one who is shocked might open his eyes widely. The same is not true for fish, but they might have their own signs.

8. A clownfish weighs about 9 ounces.

9. Fish have taste buds on their tongue, lips, and body. A large catfish can have 175,000 taste buds. A human, in comparison, has about 10,000.

10. The fish in the middle of a school is the school’s leader.

11. A recent study showed that there’s a possibility aquarium fish recognize familiar faces. In this study, archerfish were able to “spit” at a picture of one particular face from 44 different pictures with an accuracy of more than 80%.

12. Vision varies depending on the needs of certain fish. Some are colorblind, some have limited light cues, and others can see color clearly and distinctly.

13. A male neon tetra tends to be slender while the female is plumper, which is common for many breeds of fish.

14. There are more than 1,300 types of cichlids.

15. Some fish, including many cichlids, are mouth breeders, meaning that the parent carries the eggs in their mouth until they are hatched.

16. It is said that male Siamese fighting fish were bred for aggression before the 19th century.

17. There are more than 1,000 species of sharks.

18. Fishes’ ability to protrude their jaws allows them to get that prey that would otherwise not be within reach.

19. Sailfish are considered the fastest fish in the ocean. They can swim at a speed of about 70 mph.

The world under the water is truly amazing. You can learn new fun facts about fish every day based on the species, its location, its normal characteristics, and so much more.

In fact, you’ve probably heard the saying that only a small percentage of the ocean has been discovered. What will we find next?