Wow a lot of really cool ideas so far! This thing with putting water 'above' the tank by means of pipes seems totally awesome, but it looks like maybe fish don't actually swim there (they are too scared to perhaps!!). I'll be thinking about that for months to come though I bet.....
African dwarf frogs, these sound like they might be fun but I don't know if they'd be that interesting? I could maybe make a fun little diy project to make a lush environment for them to have fun in, so that's a good possibility.
As for the snails and minnows this would be such a cool idea, but I don't know and can't find information on breeding either of these. I know I can get minnows from an LBS (local bait store
) and I can get mystery snails from LFS, but I don't know if I could get them to breed or not. Anybody do this before?
I think dwarf puffers are really cool so maybe that's a good idea for a fish too.
What about planting a 10g aquarium, is that even possible?
Are there any small fish/inverts that burrow a lot? That might be an interesting thing to add too!
Loving the ideas,
Robert
However, they can be very difficult to keep with fish, and a lot of people find that unsuccessful (including me). They have different requirements (and have a hard time competing for food). The only thing I can think of off the top of my head that is both aquatic and land is a fire bellied toad. However, I know nothing about them, and don't know if they can go with fish or not. Some crabs are compatible with fish, I'd suggest doing a search on aquarium invertebrates. 
