The best tank would be the one with most surface area, so a normal rectangular one, tyhe longest and deepest (back to front measurement) u can afford ...depth also helps just to give fish more swimming space.
In terms of lightsing, if u want to grow plants, u need about 2wpg (watt's per gallon)
lilslim, I'm a 'not so proud' owner of a 10gall hex. My advice - don't get one cos the fishies don't like em. I feel realy cruel cos I have kept a pair of silver dollars in it - ignorance is definately not bliss!
i agree to with everyone but it depends on the kind of fish you plan on having have seen angel fish kept in a hexagon tank and it looked just stunning.
We all at times fall into what we think looks pleasant, while forgetting what would make the fish and inhabitants the happiest.
Raquel Welch would look stunning in my bedroom, but I am sure she would appreciate having the whole house to move about in. Have to check with Mrs Gl first though..