for a basic firebelly set up...
youll want atleast 60%water-40% land. or how ever you would prefere to do it. they are semi aquatic so spend more time in the water. for the substrate in the water river rocks are a must. small gravel like at pet stores is expensive and they can swollow it. i thought i had large enough gravel from the petstore, wrong. a fbt ate a peice then i got to the rock in the picture below. Its best to get river rock from home depot. that isnt river rock but its close enough and 90% cheaper then pet store gravel. and you should completly clean the water area and wash the rocks off once every 2 weeks.
i have the land/water area devided by a peice of plexi glass. you can mount it in place with a large ammount (to ensure no leakage) of clear silicon. you can get aquarium grade (i have been told its the same as the other stuff but more expensive), or just regular clear silicon caulking. you do not want the silicon that has mold inhibitors or any thing like that, those can be toxic. with the ammount of silicon used you might want it to set 48 hours or until the silicon smell is gone; i dont know about you but i love the smell of that stuff, lol j/k, i dont.
plants are a nice touch, if you dont really want to bother with plants, you might want to get a pothos. they are VERY heardy plants and are hard to kill. you can grow them in water, soil, and even in desert climates.i neglected my pothos plants for about 3 weeks and it looked but but after i watered it withen 6 hours it looked normal. a very hardy plant.
their water depth should be from 2-3 inches deep. mine is a bit deeper so i could put my shark pump/filter in. the filter doesnt get out all the toxins and bacteria but it does help keep the water clean and circulate it so it doesnt stagnate. some folks say a pump/filter system is unecessary, but i say it couldnt hurt. the water should be completely changed every 3 days.
now fore the land
in my picture i have a false bottom, which is where extra water will collect after watering. i had three different set ups where my soil would bcome water logged (when i had the entire area filled with soil bfore i made the false bottom in the picture). one i had a leak which caused my soil to be very watery and nasty. and the two other times i think it became water logged from watering. again people think a false bottom is unessecary, but if you plant to have moss or plants in the land section it is a must have, or the soil will become water logged.
a good cork curl or peice of drift wood is good for looks, the can climb, and it gives them a hiding spot which they need. the rule of thumb for FBT is 5 gallons per frog. so for a 10 gallon you should get 2 fbts. although, i house 3 fbts in my 10 gallon with no problems. background is also a good thing to have. the background should ideally cover three sides. this will make the tank look better and make the frogs fill more secure.
as for lighting, dont go with traditional bulbs, buy a fluorescent fixture. i got a 2 foot grow light with stand at wal-mart for $20 without bulbs. after i turned it on, the heat in my tank cut down and there was so much more light and detail then i had with traditional bulbs.
i think i covered just about everything. if you have any questions please ask. and sorry for my spelling mistakes its late and im to lazy to spell check right now 
and heres a picture of my FBT set up. which is a really basic set up. i try to change the water set up every time i clean the rocks (example, grade of rocks, plant location, etc,).

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Click Here to See My Dart Tank In The Making UPDATED 6.15.03 SPOILER! Still Needs Moss View At Your Own Risk