When selecting your tank try to maximize the surface area. One reason a hex tank is not overly desirable is that the surface area is so much smaller per gal
than a regular shaped tank.
Corner tanks are cool and take up less space per gal
with minimal sacrafice on surface area. One disadvantage to a corner tank is that given its odd shape it can be a burden to light evenly.
Go with as large a tank as possible simply due to the fact that larger tanks will have less fluxuation in their water peramiters.
As stated shrimp are good to start the cycle because your not forcing a fish to live thru this potentally deadly period.
With saltwater the oxygen level in the water is lower and even the most docile saltwater fish can be quite agressive when compaired to docile freshwater fish. For a 10 gal
I would say 2 small fish would be the max I would suggest going with. Tangs and other potentally large fish should be avoided with such small, verticly orented tanks.
You could do a 10 gal
hex if you where very cautious and kept a good eye on your levels. The book reefruner mentioned is in my view a must have for any saltwater aquarists. IT does not only go into the different types of setups and the equipment that is used in saltwater tanks but 1/2 of the book covers the different species of fish and common inverts.