The Octopus Studios' Silverfish Aquarium (see BBGadgets for bookworm joke that, I'll be honest, took me a second) is one of those things you wish you had right up until the day you get it, then you spend a couple of years wondering what you were thinking. Sure, its six orbs of sturdy clear PMMA plastic are future funky in a retro-1980s Schwartzenegger-movie kind of way, and the advertised "easy installation" of this $3,400 complete-kit aqua-sculpture is certainly believable. But the minute green filth starts to build up in the linking tunnels, or one of your gouramis goes belly up in a lower-quadrant globe, well, that's it for fun with fish. [Octopus via BBGadgets]
@sgodun: Snails are the best algae and carcass cleanup crew you could get for a setup like this, since they're hardy and breed like wildfire, given you give them real plantlife and proper lighting (do not put it in low light if you intend for these creatures to live). Plecostomus get huge and Otocinclus can be fickle to keep. Shrimp may be cool. Ghost shrimp can be had really really cheap.