Square or Rectangle AIO tank?

[tanan]

Hii
I m not that much of a newbie(have a reef tank for 8 months or so).
I m thinking of giving up my FW planted tank and nano reef tank for a big FOWLR(gonna be reef on day!)tank.
As I m no fan of sump( the noise and floods),its going to be an AIO tank.
The tank or stand isn't a problem as I ll ask my father's friends to build them for me.
I m confused about the dimensions of tank,an open top square tank with some small tangs,dwarf angels and a pair of clown and some other small fishes.Thats what I wanna have.
Now Whats the best dimensions for a tang tank(yellow,scopas or purple).
30"x30"x25"(97 G) or 36"x36"x25"(140G).or just 5'x2'x2'?
I m just thinking out loud may be.But would love to have some great ideas.
So feel free to chime in.

[danel]

I think that tangs need more swimming space so I'm assuming the longer the tank the better. i would go with the 5x2x2

[tanan]

I know that too,but an square tank sounds too irresistible to me.
So,If I cant keep tangs in a 3'x3'x2'.What are my other options ?
some of the small angels,anthias,wrasses,butterflies?
I m thinking of packing it densely with macro algae.I dont mind fishes nibbling on them but I dont want to end up with a happy Big obese fishes and no algae.
So,any thoughts,ideas?

[sailoracu2]

I've had an AIO for 2 year and I HATE it maintenance is a pain. My build for 2011 will be 36'x30'x26' (125G) with a sump that gives added water volume, just in case you over stock your tank, and yes you can keep tangs in a 140G tank.

[tanan]

To each his own I think.
I on the other hand find AIO easy to maintain.As I dont use heaters or external filters.
Might have to rethink about my big tank skimmer.But I ll go through the algal scrubbers If I have to(have run AS previously and it worked great).
And I think the problem with 14o G 3' is that it doesnt have a long swimming space needed by tangs and such highly active fishes.
I dont want to keep them in a place where they arent happy.So what other options do I have other then tangs ?
I dont wanna do an aggressive tank( no triggers,no big bully angels,no eat'em all lions and puffers).