The Fish 'n Flush is an aquarium for your toilet. According to the manufacturer's site, "Fish 'n Flush… makes a fun-fashion statement for the homeowner who wants to have something unique in the bathroom. It's $299 and fits most standard tank/bowl configurations.
Toilet aquarium (Fish 'n Flush, via Dark Roasted Blend)
Previously on BB Gadgets:
• Tacky Glass Toilet Dioramas