I think one foot matters a lot to bigger fish. I've had triggers and they loved swimming the length of the tank. If it's fish only, the right tank would be the longer one. Maybe the owner has to get more creative in rockscaping, but the fish would prefer the length.

Having a 120g with lots of fish including tangs and a trigger, I'd go the 24" width regardless :D As Tony said, you can do an awesome rock structure in the middle (thank you Jon :wink: ) with swim-thrus, and the fish can swim around, over, under.

Just my own personal observations, and comparing to the fish swimming the extra two feet in my larger tank without this "width" option as much.

If you decide to go reef later, the lighting will be cheaper as well.... :lol:

It seems i will be going with the 120g regardless. After much discussion with the 135 gallon owner, his demensions for the tank seems to have matched my friend kris's tank at 105g. It seems he had his messurements down wrong and it is actually a 105 gallon.
Thanx for all your help I will keep you posted on the result of the tank.

120 g

42"x24"x30"

FYI

L X W X H / 231 = Gal.

Which makes the 120 a 130 and your 55 a 41
and now the 135's only a 105. :roll:

hmm thats a good for the new tank then :D

bad for my current tank :(

so in the end :)

Jamie = coral guru and mathematical genius! :)

I like the wider tank myself but my opinion for any of the bigger fish would be to go with a 6' tank if possible. I chose a 5'x24.5"x24.5" tank and according to the formula; my 155gal tank is a 155.90909090909gal tank :shock: (why couldn't they just add that extra eensy bit to make a 156 :roll: ) , if I could do it over (mulligan), I'd go with a 180gal for the extra swimming length. JMO

Troy= smart a$$ :lol:

So anyways, how much would they have needed to add to make your 155.90909090909gal a 156 gal?

Ha :D I dunno, your the math expert :P

Actually, if they'd made it .03499 inches longer I'd have myself a 156gal tank :D

Cheap bastards!

PS: that would actually give me a 156.0000118939393939393939gal tank and I don't think I could afford the extra money on water changes, never mind the eye dropper.

Jamie passes the math expert torch to Troy. I'm geussing you'd start you speach something like this...

I couldn't have done it with out my...Caculator..... 8)