I understand the symbolic nature of tank one. Perfect for an umbuna tank.
Tank two hails back to the horror movies of Ray Harryhausen, beautiful.
Number three must be seen as a simplistic scene of midwater idealism. The bottom is only there because it has to be.
Ah yes, tank four. It`s grandeur cannot be fully comprehended. The driftwood convergence is perfection itself. The two pieces at right angles speak to me. The scarcity of plants, the slate table remind us of how temporal our very lives are. For this reason I am compelled to vote for number four, a self introspective masterpiece!