Contained emotions or creative juices. Are the fish in your aquarium thriving or dying? You always want your dream aquarium full of clear water and thriving fish. Dying fish suggest something in your life you are struggling to keep alive. Cloudy water can point to depression or an unclear situation. Can sometimes symbolize a responsibility you have.
If you are trying to get fish back in an aquarium, then ask yourself what you are trying to get back to normal in waking life OR what has gotten out (as far as a secret) that you wish to contain again?