I’m not crazy about the particular models here, but I really like this idea, from user littlerob904 of Aquarium Advice, of using Lego MOCs to decorate your fishtank. I have visions of a detailed layout that covers most or all of the tank bottom featuring an Atlantis or a R’lyeh theme, with fish chosen to match.

More:

• Double-whammy lighting/heating energy saving tank hack
• Gorgeous zen aquaria
• Infinity-pool fish tank
• Interactive ping-pong table / virtual aquarium