I had a 20g Long as my first aquarium when I was 11 years old.  Back then, the rule was 1" of fish per gallon, and I didn't like that rule.  So instead of worrying about any fish, I decided to make it an invertebrate tank. There was no limit to how many you could add, which was awesome.  I remember getting:

• A mated pair of Coral Banded Shrimp
• A Cleaner shrimp
• Lots of hermit crabs
• An Arrow Crab

I don't know what else I may have had in my first tank, but I do know that one day I woke up and everything was dead.  It looked like armageddon in there.  The arms were ripped off the Coral Banded Shrimp! I have no idea what happened, but I had to go to school. When I got home, the tank was gone.  Odds are it was a copper poisoning situation since we used tap water to make our saltwater back then. 

Later I got the opportunity to visit the island of Moorea, Tahiti. I swam in the lagoon waters every day while I was there, keenly observing every critter I could. I followed behind a Volitan Lionfish for 40 minutes until it finally swam away, annoyed that I was tailing it. My dad had two saltwater aquariums, which we would work on together on occasion. I remember helping him feed the predators: a grouper, a lionfish, an octopus, and an anemone.  We used live goldfish for food. 

Fast forward many years, I returned to the hobby the day I got my divorce finalized. I've been keeping saltwater creatures ever since.