Ha my first reef tank was 20 metres.My first reef tank was a 4 foot aquarium with an inch of beach sand on the bottom. A heap of live rock I got from the beach, along with the sand and seawater.
Ok not mine exclusively. My high school biology teacher was a marine nut and also lived next to the sea (literally, you could step out of the garden into the surf and we all used to store our surfboards in her shed). The school was also a 5 minute run from the beach so when we set up an aquatic society the back wall of the lab was turned into a giant aquarium.
I bet not many people can say they looked forward to double biology on a Friday afternoon, or that a mask, snorkel, gloves and net were required equipment for being in the class