When I moved to a coastal region of Florida, it opened up a whole new area to explore. I've always been a fan of the beach, but now I had easy access to both oceanfront and a calm saltwater sound (known locally as the Indian River).
It wasn't long before I had a small 5-gallon aquarium, a simple setup with just a circulator, light, and heater, and had stocked it with whatever I was finding on my explorations. The original intention was to have a temporary housing place for interesting photo subjects, but it developed into a nearly self-sustaining system. The only thing I did is replenish the water regularly, stock with various seaweeds as a food source, and watch what happened.
After I left Florida, I still used aquariums as temporary housing for any aquatic subjects that I happened to come across, and refined some of the techniques in tackling these subjects. You can find out more about these methods by checking out the macro tank project.