Christine,
I started out with a 3 gallon nano (type) tank about a year ago. It was an eclipse 3. It was great because everything was enclosed. I had about 20 lbs of
LR, 2 xenias, some zoos, a mushroom, a clown, a
BTA, and two snails. I did have to get some different bulbs than what it came with. I also had to keep a close eye on the water quality. I had it up about 7 months before I upgraded to a bigger tank. The trouble was that with that little bit of water a small evaporation can really alter everything. ie .5 gallon can make a huge impact on a total of 3 gallons but not on a tank with 40 gallons. It will just need daily attention and a lot of measuring. Also dosing is really hard to figure...you have to really do some math. BUT, all that being said it can be done and I had good luck for a while. I can tell you my
BTA didn't make it after the transition to the new tank but I think that was operator error. Everything else is still with me

Good Luck.