This is a 1/2 terrarium 1/2 aquarium I did about a year ago, I have since taken it down, but I figured I would share it with you guys anyways...
The tank was 55 gallons, it had 4 4' vhos, the only filtration was power heads and waterfalls, and suprisingly waterfalls do a great job filtering and a lot of great algae can form on the waterfalls... the tank had all kinds of stuff living in it, the water had 2 big plecos ( other misc LFS fish you wouldnt care about) it had a siren (for those of you who dont know what a siren is, its like an axolotl, mix between a fish and newt, only two front legs and frilly gills) it lived in the water and would climb up on shore to munch on mealworms, there was also a tiger salamander, some fiddler crabs, firebelly toads, and some firebelly newts.
I never knew any of this was possible, to house so many different sepcies together, and have everyone live in harmony, but I did, and it worked great. These animals will really burrow and build tunnels and caves when given the right amount of substrate and plants.

thats a big tomato plant growing on the right side of the tank, I have no clue how it got in there, I just decided to let it grow and see what happens, it killed some of the plant under it, oh well...