You could do a saltwater nano-tank (10 gallon), but, you would have to make sure everything is totally stable. I was fortunate to get good cured live rock (2 years cured), water, and fish from the same place, so when tank is setup, is stable since it all came from the same system. If you plan on setting one up, try to find LFS and purchase all the livestock, live rock, live sand, and saltwater from their system. At least its an established system with less likelihood of going unstable. Talk to LFS abouit it, they will probably rell not to do it, or go to a bigger tank. Its not really easy to do unless you do the reasearch, but it has been done succesfully with the right know-how. Salt water books are extremely helpful, "The marine aquarium problem solver" book by Tetra Press is extremely good for fish compatibility and tank needs, water quality, live rock/sand substrates, equipment setup and how they work with what setups.

miley*